Speculations, seems interesting. I'll try too!
Microsoft
They will probably be the first to launch their next console, because the XB360 surely will be on life support. It will be a hard decision that they will try to postpone the most possible. That's because they won't be able to copy Nintendo, and so will be at a loss as to what to do next. So they'll probably go for the birdmen solution : a more powerful console with a wiimote-like. The equivalent of Nunchaku or other peripherals likely won't be copied, because of patents. They will model it towards playing FPS, not like a general thing like the Wiimote is.
They will be at a loss as to how to implement pointing technology. They will go with a ultrasonic system, that will cause all kinds of issues (like poor battery life) and won't work well.
Still not understanding disruption, they will follow the advice of numerous studies they commissioned, and make Wii Sports-like, with Gamertags additions that are Mii-like, but "better", you know, with realistic faces. They will have Blu-Ray discs and will be able to play movies, they will all be HDMI and composite. They will have tons of FPS at launch, all sequels of XB360 games. They will also have a new trilogy, "Halo next episodes", in TRUE HD (TM). Where they will explain that no Halo was really in TRUE HD (TM) before, but that now, all the games will be 720p minimum, not through a scaler. They will promote a new XBL, even more complicated and confusing (what they will call 'improved'), but which will make the hardcores say wow, at least those that didn't quit gaming.
It will still be expensive, like 350 $, they will try not to make it more than 400 $.
They will go for 2 kinds of units max. All will have harddrives, like 100+ GB.
Sony
They will wait for Nintendo to release informations on their next console, as the PS3 will be in life support too, but they will use every spin possible and then more, to try to make the industry believe otherwise, added to their 10 years plan. They will then be birdmen too, trying to copy every feature they caught a glimpse of, not understanding anything about Nintendo's strategy.
Then, at a loss as to what to do, they will have a PS2 like controller, and a separate motion controlled one. These will communicate through Bluetooth, so they will boast about needind no chord between each other (and bypass Nintendo patents). They will licence the same ultrasound techno as MS for pointer functionality. Most likely, they will end up licencing Nintendo's infrared techno.
They will stay with the cell, just more powerful. They will impose a norm of 1080p games, the poor ones will be 720p.
They will introduce the "best graphics evar!!!1111one!eleven" as they will be the only ones with 48 bit depth output. Natural HDR FTW.
Anyway, it will be their main innovation... err, evolution, but they will call it innovation, or perhaps even revolution. Everything in the PS3 will be there, with full PS3 BC. They will copy Nintendo VC and have one of their own, with PS2 games. It won't be more than 350 $. They will also have 100+ GB HDD.
They will have at least 1 of their biggest 1st party franchise ready for launch.
Nintendo
I don't know what they will come up with next. But they will have all the time they need. They will keep the form factor, they will keep the simple controllers.
They won't put a harddrive in their console, it will still be flash memory. But now, they will have 8 GB internal flash memory in there, perhaps more.
They will probably have BluRay drive, but will only be able to read one layer. Perhaps they will stay with DVD though. They won't have movie playback.
WiFi will still be integrated, in the next version (802.11n or more), with WPA and all.
They will have games based on all the data they collected with their channels in Wii lifetime, with one new 1st party one, that will have all the qualities Wii Sports had.
The Wii controllers will be compatible with the new console, so the new console won't come with these. It will have a new controller, a kind of improved wiimote.
They will have 720p output MAX, and will come with HDMI output through a video port, perhaps with a composite adaptor too.
They will make a transfer option from Wii to the new console, to automagically transfer all your Wii data without effort.
The console will be 200 $, 250 $ max.
