Couldn't that just be because the bad economy is finally impacting the games industry, as people just can't afford to buy as much as before.

Yes. This is the wrong time to move to a new console altogether. Their resources would be best spent on first-party titles to get people interested in console gaming again.

Wait a few more years until your $400+ console can be launched for $200 with the games people want right there at launch.

This sounds plausabile for the first two years on the market, maybe a little less.
After that 360/PS3 systems will start to really lose steam in the sales department and games will sell a lot less more. I can still see Madden/Yearly Call of Duty pushing sales, but that's about it. Probably Activision will make two versions of COD (or push for MS/Sony to make the system backwards) and EA will make multiple versions of Madden (no surprise there).

I think it will be some time before the 360 completely dies off in sales because MS profits from each 360, where as the XBox was costing them money to keep the system on the market place.

I never really though about it before, but that does make alot of sense. But wouldn't the specs in the consoles change alot and end up costing the same, even if it launched later?

3rd parties are not always as smart and don't always use sound logic when deciding what kind of games to make and for which platforms.

No, just no... Why would you even think that? Are you a developer? Many devs say they can't wait for the next consoles to come out cuz they're bored of current gen and want something better. I keep hearing from Nintendo fans the same thing: PS4 and 720 won't provide huge graphical leap...

The image quality will be so much better than current gen, its not just about extra polygons or resolution, you're uninformed.

eh there's enough room for improvement from last gen to this gen.

Imagine bigger cities and nearly every pedestrian with its own (decent) AI. AC3 was clearly handicapped by PS3/360. Just look at the draw distance.
Other example: Draw distance in Skyrim on PS3: http://threepartstheory.files.wordpress.com/2011/11/newps3_013-bmp.jpg
360 version is only a tiny bit better.

Textures will be much much better, add to that dynamic lighting/shadows, improved physics, animations, AA, possible 60FPS and much more. They will feel like completely different games.

You think that PS3 games would not be possible on PS2, but that is only rarely the case. Most would and with the exact limitations you mentioned in the OP.

Since PS4/Xbox³ have more power they will more easily handle split screen in games. Obviously it would be the developer's choice, but a 4 player splitscreen campaign or online CoD with decent graphics would certainly be possible.
Now if you say that split screen was already popular during the PS1/N64 era I'd agree with you, but if you play these games again you will easily see that the 4p splitscreen mode runs barely above 20FPS across nearly all games. The same could be done on PS3/360 but would be unacceptable by todays standards, that's why not many devs are doing it.

Also imagine with possible keyboard/mouse support, games like Total War or Starcraft 2 would be possible.

Is there an 8 core CPU in PC gaming?  No.

The majority of PC gaming computers are dual core with a few being quad core.  Having variable AI isn't as easy as having variable graphical detail.

As more and more people purchase quad core CPUs and as 6 and 8 core CPUs become the norm than you'll see PC gaming offer AI levels that differ from the console.  Until then, developers will develop for the lowest common denominator, which is a dual core processor. 

Ok, it's not everything developers say they want... but I mean enough to express the game they have in mind. Can they make sweeping open worlds, or intense atmospheric jungles, or truly frightening horror? On PS1 the answer was no, on PS2 the answer was kinda, on PS3 they aren't really being held back on scope or immersion or clarity. Yes, everything will look a little nicer on PS4 but it doesn't change what's possible.

Don't confuse me with a 'Nintendo fan'. I hope the Wii U sells zero units. It doesn't matter to me how well or badly PS4/720 sell really.

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@Barozi

I don't think people buy games for draw distance.

The other major tech change with a real effect on games that forced the PS2 to retire was online multiplayer as a social experience.

I don't know that core games need local multiplayer any more. Mario Kart and Wii Sports do, but would people have friends round to play split screen CoD or Halo? That said it IS the kind of possible/not possible thing I'm looking for with next gen. What else do devs mean when they say they can't wait for next gen?

1.6GHz AMD 8-core is the rumour? That's weaker than a 3.3GHz dual-core CPU one might buy for a gaming PC.

You're mistaken if you expect PS4 or 720 to be stronger than an average recent budget-gaming PC.