No Nintendo handheld has sold worse than its predecessor either, look at the 3DS numbers.

I'm still not sold on the PS4 selling more than the Wii, this gen will be a lot shorter and price reductions won't have the same impact on a product that released for a 600$ retail price versus one that released at 400$; the great changes might come at around the 250$ mark in most cases but in the PS4's case; that might be a little too late, developing markets are not the same cushion any longer, they are following the trends of mature markets and moving towards more convenience gaming and fringe titles for more casual customers (Buzz, Singstar, Rock Band etc.) practically don't exist on the PS4 (or One) and those that do are not doing so hot.
Look at the PS3 as well; it is moving super slow compared to the PS2 in these markets and in the twilight of its life, at this rate it'll be lucky to sell 25 million after the PS4 released where the PS2 sold in excess of 50 million.

Of course; the PS2 was market leader and sold a lot more but there is no denying that developing markets account for a lot less cumulative sales; it's not like they're buying 360's or Wii's either...
The market has changed and the fast-paced consumer electronics market will be harsher to static devices such as the PS4, One and Wii U than it ever was to the Wii, PS3 and 360.
In the middle of the 7th gen, there was a splintering of the gaming industry and market and several forms of gaming took of in popularity, this is bound to hurt traditional devices in some way and I believe it is (again; look at the 3DS, not to mention the poor Vita).

The basic reasoning behind it is the assumption of a greatly changed electronic entertainment industry since the start of last gen. This includes:

- Shorter hardware cycles (see smartphones, televisions)

The only impact smartphones have had on the industry is that it has taken away much of the casual market for handheld devices.  This hasn't just automatically made people want to replace everything they own after having it a year or two.  Otherwise, everyone who wanted to jump onto this gen would have done it by now.

- People willing to pay more(hence more early adopters -> frontloaded gen)

$399 was just a great price for the PS4 (compared to $499 and $599 for PS3), hence why so many people bought it.  This really has no affect on total sales, just affects the time when those who would not buy it for $499, but instead wait til it was $399, got it. Once the PS4 hits $299, you're going to sales get a huge boost, again.

- Move away from dedicated devices(move to converged devices)

19M+ people bought the PS4 in less than a year in a half.  If that doesn't say people do want dedicated devices, I don't know what does.  Of course, ever since the PS1 theses consoles have not been just for playing games, so they aren't truly dedicated devices, in the traditional sense.

- Japan not giving a fuck

Yes, the home console market decreased in Japan in favor of handhelds and mobile phones.  However, we still don't know what the PS4 is going to sell like there since 3rd parties haven't thrown their full support behind it, still making games for older systems.  It looks like 2015 is going to be a better year there for the PS4.  There's also the fact that other markets have opened up and/or become bigger, making up for shortcomings in Japan.

- casual's complete abandonment thanks to mobile

While casuals helped push the PS2 to ~160M, they sure as hell didn't make up the majority of its audience.  It still would have sold 100M+ without them.  There's nothing that screams casual about the PS3, except maybe Move, but it still will reach 90M, even with great competition from 360 and, for the first few years of its life, the Wii (which took the vast majority of casuals.)  The PS4 is going to outperform the PS3. 

Stuff like that and some wishful thinking. Of course these are just assumptions based on observations outside the console industry and could be completely wrong.

If you go by these assumptions, the PS4 having a great first year means absolutely nothing and rather seems to confirm frontloaded behavior. So yeah, it's actually really easy to belive PS4 will not reach 100m with the right mindset^^

Ps3 and Xbox 360 was doing good before Sony and Microsoft decide to kill it by releasing ps4 and xb1 and keep both consoles expensive.

When you see the numbers of cross-gen games it's difficult to believe 3rd party want a shorter and i don't believe both constructors want to release a next gen without third party support.

That won't happen unless they want to go bankrupt. 10 years is 4 years too long.

No Nintendo handheld has sold worse than its predecessor either, look at the 3DS numbers.

I'm still not sold on the PS4 selling more than the Wii, this gen will be a lot shorter and price reductions won't have the same impact on a product that released for a 600$ retail price versus one that released at 400$; the great changes might come at around the 250$ mark in most cases but in the PS4's case; that might be a little too late, developing markets are not the same cushion any longer, they are following the trends of mature markets and moving towards more convenience gaming and fringe titles for more casual customers (Buzz, Singstar, Rock Band etc.) practically don't exist on the PS4 (or One) and those that do are not doing so hot.
Look at the PS3 as well; it is moving super slow compared to the PS2 in these markets and in the twilight of its life, at this rate it'll be lucky to sell 25 million after the PS4 released where the PS2 sold in excess of 50 million.

Of course; the PS2 was market leader and sold a lot more but there is no denying that developing markets account for a lot less cumulative sales; it's not like they're buying 360's or Wii's either...
The market has changed and the fast-paced consumer electronics market will be harsher to static devices such as the PS4, One and Wii U than it ever was to the Wii, PS3 and 360.
In the middle of the 7th gen, there was a splintering of the gaming industry and market and several forms of gaming took of in popularity, this is bound to hurt traditional devices in some way and I believe it is (again; look at the 3DS, not to mention the poor Vita).

Except they're both bigger than Nintendo and if the people here have a lot of faith in Nintendo then it can only make sense that they'd be the least likely to go bankrupt ...