I doubt a new console will be launched by either Microsoft or Nintendo until at least November 2011 at the earliest.
For Microsoft, Natal is coming out this year. So, there is no way that they would release a new console (XBox720 or whatever) in 2010, and only in 2011 if Natal completely flops, 2012 seems most likely. However, a rumored slim model is very likely this year, and may be worth waiting until E3 to find out about. Considering you are thinking about a Wii too, you could easily get the Wii first, and hold off on the X360.
As for Nintendo, there is no reason to wait to buy a Wii. If there is a sufficient catalog that interests you, buy it now. No Wii HD will ever be released. A true successor to the Wii won't be released before November 2011. The 3DS comes out in FY2011 (before March 2011) so Nintendo wouldn't release a home console in the same year. Even by TheSource's analysis (news article) he doesn't think Nintendo will release a new home console until 2012. Also, as stated, there are some good bundles for Wii right now.








