This way the PS4 would get a headstart to the next next Xbox, since it could be a more powerful console, it might be next next gen in the end

So there won't be a nextgen Playstation.
BUT I think SONY and Microsoft are planing to release their next consoles pretty much in the same timeframe, because they need the competition and they need to attract third party developers, which would never release their game on two different consoles, if the specs are that much different. But we will see, lets just hope GT5 is released this year!
Looking at it from a first party standpoint, MS is in some real trouble. When Kinect tanks (and it'll tank HARD), they'll realise they've got nothing left. Their big-name FPS developer (Bungie) has gone to Activision, which is an issue in itself considering Kottick's greed for copious piles of gold, including MS's money from their XBL system. With the next few COD games looking decidedly meh after the people with talent bailed on them, they've got maybe 1 more title before even the name CoD is worthless.
With First Party games it's already looking to be a bleak year, without Eye-Toy - I mean kinect they've got Reach, Gears3, Alan Wake....and that's about it. That's a whopping 2.5 games; the ending of Alan Wake should be available soon for paid download on XBL sometime soonish.
Sony at least has always made consoles that keep getting better and better, the latter PS1 and PS2 games were awesome, and it always had a nice list of good games right up until the day they stopped making the console. Move might work, but that's still a bet of long odds. Even then, they've still got Blu-Ray and PlayTV and what not, so from a home entertainment standpoint they've already got a home. to fall back on.
So, considering all above, the NEXTBOX would need to be out within maybe 3-4 years at most - because at this rate it'll have less games on sale than the Taco does.
This bring's me back to your post - all of that will throw the generations off 50% between MS and Sony (providing MS is still in it for the next 2 gens). Now, the closest thing we've seen to that are Wii ports of PS3/360 games, from a technical difference standpoint anyway (wii is a last gen console with WiiiMotes).
Though it would give rise to the possibility that GT6 MIGHT be finished in time to be a launch PS4 title (if they hurry up). And it would give GT5 an incredibly long life cycle, provided they don't rush GT6 onto the PS3.
Think of it, is it possible for a 4 year old game that keeps up with the new releases (GT5 launches this year, and updated till the death of the PS3)? Well, Prologue is still the best looking racer, so it was possible for the last 4 years at least, which is something special when you consider how fast visuals are advancing.
That said, I th
ink they'd have to all have cockpits, I don't think 200 cars will hold me over 5 years in the future