That would seem borderline unbelieveable because the trend seems to that this generation will see a decrease in the number of gamers.

ps4 - 90 million
xbox one - 85 million
wii u - 50 - 60 million
3ds - 140 million
vita- 30 million

There are a few factors I considered when coming up with that 'outragious' figure. Here's some of them:

1/ It's form factor is already what you would consider 'slim' (not much of a facor though) it just suggests to me that they'll find in easier to reduce the size and price much quicker.

2/ It has the same buzz that the PS2 had and that sold rather well

3/ The momentum going into next gen is fantastic and far exceeds that of their closest rival

4/ It's releasing alongside the competition and not a year later (giving them equal chance at mind-share this time around)

5/ It's a $100 cheaper (this will only help boost momentum for now though)

6/ It looks damned sexy and it's clearly built as a centre piece to impress your friends with (the envy factor)

7/ The controller has been getting incredible reviews and I believe that to be very significant

8/ I believe it's going to be on the market much longer than the PS2 or the PS3 (significant factor)

9/ The Vita is going to be a compelling reason to buy a PS4 (and visa versa) and so is VitaTV. (not a huge factor but certainly a help)

10/ The new base they built in America shows clear intent that they want to dominate that region (it won't dominate it as much as Europe)

11/ The Indie scene is going to be BIG, and I mean BIG. Sony will keep close relations and hire some of the more talented teams.

12/ Emerging markets will become far more relevant as will CHINA!

13/ This time around 3rd party games will favour the PS4 as will first party games (but much more so than on the PS3)

14/ It's easier to develop for and more powerful than the opposition which will mean seeing the differences much earlier in the lifecycle

15/ Their developer relations is much much better and they're clearly investing heavily into making sure that continues

16/ They've created a team specifically for localising Japanese games and visa versa (meaning they can distribute content better to suit the current trends)

17/ It's a games machine foremost (at least that's the message Sony have been able to convince people of)

18/ I believe this could be Sony's last console and that the next console will be something along the lines of the VitaTV (using Gaikai)

19/ Because of Gaikai, the PS4 will be an alternative for next gen to bridge the gap between physical games and PSTV (streaming only)

I predict 105 million

i think the PS4 could sell as much as 1 million by december 2013 and then on to 120 million by 2020 when the next gen is announced, dont expect disc media though and HDD's will no doubt be 1000TB and cost less than $100, more than enough for the next generation.

My predictions will be bold and impracticable seing as the world is facing an all-out war be it economic warfare, armed conflicts or both.

By preorders trend I'll go with 18 million sold the first year, and 150 million throughout it's lifespan, because I'm quite sure there are more gamers now than in the PS2 area, and competition seems to be weaker this time around with Nintendo going rather downhill and MS loosing a lot of momentum.

70 million for ps4 (maybe 80 million optimistically) but it'll still most likely still lead this gen...I just think the markets gonna shrink considerably. It's gonna take a lot for any game console to be a must have item with your typical consumers (I mean outside of core gamers) in the current climate and I doubt that's gonna change.

I think ps4 will have a strong start and continue to make momentum and reach 80-90 million.
Once xbox one gets a price cut and has recovered from bad press also if microsoft continues delivering games xbox one will sell around 90-100 million and maybe the generation leader

90mil

PS2 also had no competitiion for about 10 months and this is probably one of the reason it gained alot of its momentum in its life. 

I don't know about you but $400 still seems rather expensive for the average consumer.