Hi,
I shouldn't think there'll be a problem. HDMI 1.2 can do 1080p24/50/60 and multichannel audio. 1.3 adds support for resolutions above 1080p (not a problem for most people), support for 100Hz/120Hz refresh rates (again not a problem for most people) and possibly even higher bit depth colour (not really a problem for anyone anytime soon). Plus most decent quality HDMI 1.2 cables will meet the 1.3 specs anyway, as long as were not talking about really long cables. Anything up to 3m should be fine.
From what I hear you can get 5.1 over HDMI from the xbox, but I don't have one so I can't confirm this.