There are two things to consider here.

First off, the Wii was going at a faster pace than the PS4, and that reached just over a million.  I know Wii was a fad and blah blah blah, but the Wii's decline wasn't excessively fast until 2012.  Factor in also that by the time the Wii starts slowing down, the PS4 will have a 10 million plus gap to close.

Secondly, this generation may not last as long as previous ones.  Nintendo's already launching a new console which can take some steam away from PS4, and if XBox doesn't start making up some ground, they'll probably be inclined to start the generation early.  Sony's systems still tend to have better legs than their competitors, but the PS3 hasn't lasted as long as the PS2 did.

150 million doesn't really seem possible.  100 million does seem likely, but it's far from a sure thing.  It seems like all three companies are going to be releasing some sort of new hardware, which could potentially change the sales trajectory going forward.  

So.. Neo is nearly official + Yoshida has expressed doubts about a PS5, and there are still people who think the ps4 will end 2-3 years from now and be replaced by PS5? Lol. Unless the industry as a whole takes a massive downswing (for whatever reason) that forces the 3 into a radical shift that requires all new/different devices, expect the "PS4" to last until 2025 or longer
PS4 2013
PS4.3 2016/17
PS4.6 2019/2020
PS4.9 2022/2023
PS? 2025/2026 (new games no longer support 2013 ps4, probably). Won't be called PS5 but will be seen as such by the community

1) I dont believe this generation wil be shorter. It ll be much the same.

2) NX will probably be between PS4 - PS4 neo level of performance. Its just late to the party.

No one cares about gens, much less what gen the new nintendo console is. They care about is what the games look like and play as.

Xbox One ii (one two) will be a stronger Xbox One.

We have 3 new consoles comeing out soon. That to mean doesnt sound like a generation being short.

(it sounds like we re still in the beginning of the gen, or atleast closer to the beginning than the end)

3) PS3 didnt ever get to the cheap prices the PS2 did.  PS4 was buildt to become really cheap over time.

4) Imo unless something goes really wrong, 100 million sales seems like a sure thing.

I hope it does, but I doubt it.

It won't.

I think it will outsell the PS1 but I don't know about the PS2.

You're assuming that the NX will fail, which based on what we know, is not a safe assumption.  I really doubt Nintendo is going to release a console that is essentially the same as a PS4.  The comments of executives point to some sort of gimmick which may or may not catch fire.  

We don't exactly have 3 new consoles coming out.  As far as we know so far, we're getting two revisions and one new console.  That's a bit different.  Surely, these were made with the intention of extending the generation, but that doesn't mean it will work.  In particular, if Microsoft keeps falling behind the PS4, then they'll be inclined to begin the next generation earlier, assuming they don't want to drop out of the market outright.

We really don't know that much about XBox 12 or Neo.  Obviously there won't be huge changes in hardware, but there might be some interesting new software feature.  XBox One also has their Hololens thing so we'll see if that helps them gain so momentum.

Like I said, I don't think 1 million is particularly unlikely, but untill we have some more solid details about other things going on, it's way too early to call it a sure thing.

My thoughts on that is PS4 will struggle to outsell PS1. It needs another 60 millions units to do so. So at least another three years with 20 million units sold each. I guess we will see PS5 hit the shelves right before..

Even if the PS4 goes on to sell 140m, I doubt MS would have any issues if say the Xbox One ended up around say 60m.

"Inclined to being the next generation early."

Why? If you ignore the Wii, how many Nintendo consoles have ever sold more than 60m units?

"assumeing they dont want to drop out of the market outright"

wow... You know theres more to a bussiness than just being #1.

As long as MS is able to make money doing it Im sure theyre fine with just reaching say 60m units sold.

I dont think you should get your hopes up for a new console before 7nm technology is ready and affordable.

That probably wont happend before 2019.

For a point of refrence, the PS3 sold roughly 7 million units since the PS4 came out.