I don't remember talking about graphics at all.
More powerful machines means more room to improve gaming itself, not only graphics.

What I don't understand is why people DO believe it will be as long the last gen, with 4/5 gens saying it will be 5 to 6 years lifespawn and 1/5 gen saying it will be 9 to 10 years lifespawn. Data is telling us that it have a 80% probability of being 5 to 6 years, I'm just going with it. But yes, that same data was giving us a 100% chance to it to happen last gen and even so last gen went off it, so it happens, but it's atypical.

Game developing always get more and more expensive, it's not safe to say that just because it's getting more expensive again it will take a longer gen again.
PS4 is a point against it. With so much people already jumping to it game sales are bound to increase too so one thing go against the other.
As Destiny is too, a really expensive game (maybe even the most expensive ever) that is bound to pay itself with ease.
Another point is again the mid-range tech that the consoles have as I have said, which is good tech but don't seems like it can endure as long as last gen could.

So I'm not saying it can't happen again, but I just think it's unlikely.

People compare the PS4 to the Wii because they've been the consoles with the strongest launch periods out of each generation, and the PS4 is selling less than the Wii did.

I highly doubt the PS4 will crack 100 million unless this generation stretches on for 8-9 years. It's had a strong start, but when you compare all of the current-gen consoles to their last-gen predecessors at the same point in time, people aren't buying into this generation anywhere near as quickly as they did the last.

I did these calculations on another site about a month ago, though they're still fairly current:

PS4: 10m vs. PS3: 5m
One: 5m vs. 360: 5.5m
Wii U: 7m vs. Wii: 32m
Vita: 9m vs. PSP: 29m
3DS: 44.5-45m vs. DS: 55-60m

The PS4 is the only console tracking ahead of its direct predecessor right now. The XO and 3DS are tracking slightly behind, and the Wii U and Vita are tracking way behind. When you add everything together, it suggests people are either content with the consoles they bought last gen, or they've moved on to other devices like iPad, smart phones and even PC. The PS4 has also been riding a wave of insanely positive press whereas the PS3's reception was mostly mixed until a couple of years in; I suspect in a couple of years time, the PS4 won't be tracking so far ahead.

I think it's definitely possible that the PS4 will still go on to be this generation's best selling console (after the 3DS, anyway), but if so, I'd expect it to hit between 60-80 million. I don't think any console is likely to get much higher than that in this generation.

This pretty much sums up my thoughts on the matter.  I'm surprised...but not shocked...to see so many people so bullish on the potential for the PS4.  We are in a much different market than the previous generation.  Excluding tablets, smartphones, etc...the economy of today nowhere matches the economy of 2005-2008.  

Really...to move outside this window the PS4 is going to have to release a game or peripheral that dominates the interwebs like an ALS Ice Bucket Challenge.  I just don't think that's likely this time around.

Nothing say this, as nothing says the opposite too, but the older data we have are, after the 3rd gen, which is what lead to what gaming is now is:

3rd generation started in 1983
4th generation started in 1887
5th generation started in 1993
6th generation started in 1998
7th generation started in 2005

So the years between the gens are 4, 6, 5, 7, respectively, BUT that don't represent the actual scenarios of the 3 gaming brands we have now + Sega, the four really relevant brands this market had after the 3rd gen, some other company consoles as Atari, 3DO and PC-engine hold some of those numbers.

Nintendo released the NES in 1983 at the very same day Sega released the SG-1000, both in Japan. But the later was quickly replaced by newer models until the Mark 3/Master System finally took steam and put Sega really in the console market, in 1985.

So let's consider Nintendo started the 3rd gen with the NES in 1983.

The next consoles from one of these 4 was the Mega Drive/Genesis by Sega, and was released in 1988.
What leaves us with 5 years from the start of the 3rd gen to the start of the 4th gen.

Then the next console from one of those 4 was the Sega Saturn, released in 1994 and the Sony PlayStation, too in 1994.
What leaves us with 6 years from the start of the 4th gen to the start of the 5th gen.

Then again, the next console from one of those 4 was the Sega DreamCast, released in 1998.
What leaves us with 4 years from the start of the 5th gen to the start of the 6th gen.
Then the next console from one of those 4 was the Microsoft XBOX 360, released in 2005. What would leaves us with 7 years this time, but the Sega DreamCast was discontinued quickly as Sega jumped off from the consoles market, which leaves us with the Sony PlayStation 2, released in 2000 as the older full 6th gen console.
And now if you want to really disconsider the DreamCast you can claim that the 5th to 6th gen gap was 6 years.
What leaves us with 5 years from the start of the 6th gen to the start of the 7th gen.

So that would be a gap of 5, 6, 6, 5 years respectively until the last gen. And that's a hint of how long gens usually are.

Actually considering the DreamCast we have a gen with only 4 years... that's even more relevant to my argument. So no.

But comparing the consoles by company is also relevant.
XBOX to XBOX 360 also have only 4 years. And XBOX 360 to XBOX ONE have 8 years.
NES to SNES 7 years, SNES to N64 6 years, N64 to NGC 5 years, NGC to Wii 5 years, Wii to Wii U 7 years.
SMS to SMD 4 years, SMD to SS 4 years, SS to SDC 5 years.
PS1 to PS2 6 years, PS2 to PS3 6 years, PS3 to PS4 7 years.

So you can see how this last gen was atypically long.
XBOX doubled it lifetime, went from 4 to 8 years.
Sega was not present and it was ever 4 to 5 years.
PS went from two 6's to 7 years.
And Nintendo went back to 1980 numbers... but wait, "I can't use 1980s to prove what happen" so Nintendo went from to 5's fives to 7 years.

No matter how we try to see it, last gen was way longer than what the others gens where. And it's not safe to expect this again.
It had one only seven years peak back in the 80's that actually where the console that could bring the market back to life and it was expected to endure long.
Gens were ever 4 - 6 years. Now they went to 7 - 8 years.

And again, I doubt the PS4/XBO will remain relevant in the market for so long again.
Nintendo needs a new console quickly, and it will probably happen between 2016 and 2017, so again 4 - 5 years.
Microsoft is beaten by Sony so hardly with a alligned launch and losing so much marketshare that I doubt it will ever try it again, 2017 will probably see a new XBOX, so 4 years.
And Sony is the only that have no need to rush to a new gen, but with both competitors doing so, 2018 at max we may see the PS5, so 5 years.

You can even give one more year to all of them to they have more room to grow, and we will still have the normal 5 to 6 years generation.

Oh I'm sorry, you are right it was six years.

But seems like we have a missundertanding here, I never said PS4 can't go over 100M with a normal gen lifetime as the PS1, PS2 and the Wii, I'm actually saying it will be at 120M by the end end of it's life with a gen shorter than the last gen.

I'm saying I doubt this gen will endure as long as last gen, and PS4 will not have the same gigantic legs PS2 had so I doubt it go to 160M like the PS2 did.