Just about ALL motherboards and CPUs are 64-bit capable except for the real budget parts and maybe some notebooks. What 64-bit gets you is more usable memory so the thing you want to look at before buying is the maximum memory spec. Most boards built for 64-bit use will have 4 dimms slots and spec out at 8GB max (mainly that's a practical max since there aren't any/many 4GB dimms availalable).
As near as I can tell there's NOTHING going on with AMD/ATI parts. It was just that AMD was sponsoring some Vegas events at NAB. They sponsored non-Vegas things too.
Go ahead and wait for 8c just to get a sense of whether the slower AMD quads are more stable than the intel quads, but my sense of things is that it just doesn't matter. If you're upgrading, buy something that supports a fast quad and 8GB of RAM. Consider any cards you might want (Kona? BMD?) and make sure you have the slots to support one.
They're probably on a release schedule so they're shooting to release it according to a plan. God only knows what that plan would be. In the mean time it'd be good form to get their one or two big snafus working for a month or two so that existing users might think the next version will also work. As it stands, they need to get 8c out and have some content users out there.