One thing to consider is that it will take 18 to 24 months to market a new console to publishers before you release it; this means that if you're releasing a new console in 2010 you'd probably begin marketing after holiday season 2008 (for 2011 you'd start after holiday season 2009).
It's likely that Nintendo will be aiming for 2011 because winning or losing they tend to release their consoles on 5 year cycles and I suspect they will have reached nearly the maximum market penteration the Wii can successfully achieve.
The other two companies releases will mainly depend on how much money they're losing and their potential to recover lost ground ...







