I think it's a safe bet that yes Sandy Bridge will arrive and yes it will make its way to the Mac Pros. If by waiting "5-6 months", you mean that you're ok until 2012 or so, then sure, wait for it. If you actually need a computer sooner, then I wouldn't hold my breath.
The iCrap is Teh Most Important Thing to Apple, followed by the MacBooks and iMac, with the Mac Pro, over there, around the corner, just step over the pool of vomit and walk down the dark alley, then wait patiently [years pass], and it'll get updated.
Seriously, the Mac Pro is just not making the tippy-top of Apple's URGENTLY UPDATE SOON list, ever, lately. Personally, I'd like them to issue an update every other month, but checking back in with the real world and how my Apple stock is doing, I kinda understand why things are the way they are, and I don't lose any sleep over it.