I want to write a response to this before too much time passes, and I think it might be a somewhat controversial reply but I'd like to post this none the less. I've written what I'm gonna write (more or less anyway) in a few places the last few years when the topic of next gen comes up and I've caught some hell for it.
Next Gen...honestly and seriously this is what I think will happen. Now, I don't work in the industry nor do I have industry sources but this is what my best guess is based on stuff I've followed and read. Just to start, if I'm wrong on what I'll write about Sony I'll gladly eat my words later but I think at least in their case we have a clearer picture of where they're aiming to go shorter term.
I want to contribute an actual, constructive piece to the thread as opposed to some baseless answer with nothing to back it up.
The controversial statement: I do not believe Sony will launch a traditional home console next gen. I'll give my explanation why below.
First to get Microsoft and Nintendo out of the way.
Nintendo: Everyone knows about the Wii U, Nintendo themselves confirmed it so it's not speculation anymore. I do believe they will launch it next summer or Fall BUT they've probably had to go back to the drawing board on at least a few things. When exactly it launches will depend heavily on how much re-working they want to do. They'll almost certainly be trying to get the point across on what it is a lot better and show why it's a necessary leap up from Wii. I personally had no problem with the unveiling..I don't know if people had a problem with it per se but those who were actually there seemed to be confused on some aspects of it. They may re-work the tablet controller to some extent, I imagine they're looking at some kind of optional traditional controller support along with the tablet controller. They're going to have to deal with online/online infrastructure as well. I'm not big on online gaming but their current plans have left many underwhelmed so they're probably trying to figure out how to get to the point of "unified online structure" as quickly as possible. Will lightning strike again for Nintendo? It's simply too early to tell. I think we'll have a better idea on it's more immediate impact at launch when they're ready to show first party, EAD stuff. Could go either way but even I'll admit they're gonna have a much tougher time of it next gen.
Microsoft: I think the evidence and writing on the wall are clear, and they will release a successor to the 360. Only question is when. I do think, however, in the more distant future their gaming focus will center completely around Xbox Live and eventually concentrate on expanding that via PCs since they can get even more users that way. Microsoft has two big issues going into next gen. One: Avoid another Red Ring of Death fiasco at all costs. Doesn't matter if they make good profit every year, what matters is on a PR level they simply cannot afford a repeat of that. If it happens again I honestly think they're done with consoles but I think even they wanna avoid it again too. Two: They're gonna have to come up with games outside their reliable stable of Gears, Forza and Fable. They're all great series but it's gonna come to a point of you can take the series' only so far. Their big challenge will be coming up with games beyond those that can be real hits.
Sony: Now for my controversial statement. Watching Sony this gen I had my doubts already if they'd release another home console. With Vita coming however I have a better idea of where I THINK they're going. I do not personally believe they will release another home console-a PS4-anytime soon. Why? With Vita this much is clear..they're heavily pushing Vita/PS3 connectivity and interaction. Start a game on Vita, continue later on PS3 and vice versa. Vita is supposedly comparable to PS3 in power and tech so having a portable device that compliments the PS3 is a sensible next step. The PS3 has a lot of horse power as it is so they will push that and work well together. Secondly the whole PS3/PSP/Vita remasters thing tells me they're trying to go more in the direction of two pillars that will consist of Vita and PS3. Sony has had an awful past 5 years..PSP launched..had a great start..success in Japan, the West not so much courtesy of homebrew/piracy. PS3 launches at an insanely high price..very slow first few years..just now getting to where you can say "I'll buy one, now there's a good library of games". Just when it looked like things were finally going up for them they get hit with that whole PSN hacking. Everyone, here's the deal with that..I don't know what it costs exactly to develop a a game system but I know this much. PSN could NOT have been cheap to design, implement and maintain. A huge chunk of "PS4 R&D money" had to have gone toward rebuilding and strengthening PSN after that hack. With all those things happening I think they originally had planned on a traditional successor but in the middle of all this the question turned to "What can we do that's a good middle of the road compromise..something between a PS3 and a successor that will be a less risky investment?" Their answer appears to be Vita. They will be heavily pushing/promoting PS3/Vita connectivity, interaction between the two and how you can start a game on Vita, continue on PS3 and vice versa. I also think this due to..well basically PSN 2 on Vita..they're finally implementing features people wanted and streamlining it more. Vita is a less risky answer for now..launch Vita, get it off the ground, engineer PS3/Vita aspects, promote game development for both..and once they're more on their feet and can take a bigger investment that's when I believe PS4 will come..I just don't think it's gonna be for several years. They took way way too hard of a beating this gen. They don't want to exit the industry but at the same time they've gotta be incredibly hesitant to take a mega PS3 level gamble again.
Just my 2 cents. If I end up wrong that's okay but honestly with Sony especially that's what I'm expecting as of right now.