If the PS2 has taught us anything, we have grossly underestimated the lifespan of a console. Ultimately, the PS2 sprung so far ahead that it effectively killed the other consoles, forcing those companies to ready their guns early. In turn, it forced Sony to upgrade. It essentially prematurely killed off the last generation.
When one looks at the cost of developing a new console, it may end up being better to wait a little bit. Sony is in the red. Microsoft might be too, and if they arent, they just dug themselves out. What financial reason do they have to force another console on us when they can sit back and let this generation carry on longer?
There isnt one console sprinting ahead to really force the other companies to the drawing board. So I think we can expect a longer generation. This means that the 3rd party companies will start looking at what their next round of projects are. To me, the wii and 360 are pretty safe bets for putting games onto. The PS3 is a sort of enigma. It seems that if a 3rd party puts the effort into making a AAA game for both the 360 and PS3, PS3 version will be fine (COD4 and AC atest to this). However, if the company doesnt have the resources to develop an upper teir game, I can see those becoming 360 exclusives.
The true wild card in all of this is if companies believe that Sony can put up a good fight. As I see it, there are 2 major bonafide system systems in the pipe line for them. That is Final Fantasy and Gran Turismo. There is a distinct possiblity that those 2 games could hit in 2009. If I'm Sony, I'm making sure that those games are coming out this year. I realize that Sony has a bunch of amazing games coming out this year (I'm probably going to get all of them) but they arent the system sellers that Halo or Mario are.