Prediction: The US launch is very subdued, but the Japanese launch is very well received.
Year 1: The Wii is a distant third in the US, doing similar to what the Cube did. The Japanese have embraced it in a significant way, and while the PS3 saw some strong early adopter numbers, most of the people who really wanted/could afford it got it early on. Wii sales going forward are vastly higher than PS3, though at this point the installed base is pretty well split.
Year 2: The Japanese market share shifts to Wii in a big way. The major Japanese companies start emphasizing the Wii, as the PS3 gradually becomes a high end niche system seeing less and less support. The US shows the 360 holding a firm lead, with interest in the PS3 dwindling as fewer big new titles get announced. The Wii is still a distant third, but the huge pipeline of Japanese games begins to attract a lot of interest.
Year 3: In a stunning development, a major Japanese studio, experiencing flagging earnings as it's critically acclaimed PS3 blockbusters see less and less consumer interest drops PS3 support entirely to focus on the Wii. Sony announces a major pricedrop at E3 2009 and a Wiimote type controller, but the Wii steals the show with an unprecidented level of original support from Japanese devs. The Wii becomes a virtual monopoly in Japan, with Wii ports becoming the bulk of the major releases for the PS3 going forward. The 360 is tops in the US, and the Wii is the fastest growing market share.
Year 4: Microsoft announces the Xbox 720. It also announces that it was no longer support the Japanese market moving forward. They release impressive specs for the system, but refuse to show the controller until closer to launch. The Wii quickly moves into #2 in the US, and Sony becomes a worldwide third. Nintendo announces the codename of it's next system at E3 2010. Sony surprises everyone by not even talking about the PS4... amid speculation that increasing losses may have Sony corporate rethinking it's video game division.
Year 5:
Microsoft launches the 720. Though the controller is shaped like the original Xbox controller, it has no inherent buttons on it. Using new advances in organic semiconductors, the console defines buttons and controls in real time and varies from game to game. The buttons appear "painted on", but a force feedback system allows the user to feel as though he's pressing a button when one is touched. The button display system can also be used to display a small touch screen display on the middle of the controller.
Nintendo displays the Allso Wii... it's new system. The hardware specs resemble a souped up Xbox 360, but again, the news is in the controller. Keeping a Wii-esque nunchaku controller for basic input, the system also adds the first commercial neural interface. The standard model system displays on a television, but support is also announced for an optional stereoscopic headmounted display with headphones and mic that connects to the neural interface. While in most games the display only functions as an HDTV, Namco-Bandai jumps onboard early by announcing a fully-immersive MMORPG using the .Hack// license.
Sony shocks the world by announcing that their new system, the "PS For" (avoiding the expectation that a numerical sequel would have) will be a joint venture between Sony, Panasonic, and Philips. Essentially, the system is a smaller, cheaper version of the PS3 marketed primarily as a BluRay player slash PVR. Advances in storage and compression technology allow Sony to offer PS1 and PS2 games for download on their own download service. PS3 games will be rebranded as PSF games, although old PS3 titles will still play on the new system. The much smaller form factor and sensible price makes it a popular "second console" for Japanese gamers, though a large number of people buy the systems simply for the PVR features and BluRay.
Sammy Corporation announces it's own Japan-only system a year later (two years after the 720's launch). Through a licensing agreement with Microsoft, the system is basically a 720 with a smaller form factor (though for licensing reasons the two are not compatible). Sega continues to release "ports" for both system (which are really just regional conversions). In a deal to help finance the launch, Sega's PSF and Wii-line studios are spun off as a private company, 40 percent owned by Sammy, 40 percent owned by Nintendo, and 20 percent sold at an IPO. The studios have limited rights to use Sega's properties for new titles and also retain ownership of all of Sega's back catalog of games released on Sony or Nintendo systems.