talking to Amye and others at the D7CX sprint that happened over the weekend, I think most believed that ubercart 2.0 should be directly ported to D7 per the D7CX initiative. Getting a redone 3.x ubercore + all the modules will take much more than the roughly 5 months before drupalcon SF, and 2-3 months before D7 is released.

I just completed the alpha release for the coder 7.x port, and I think once 2.0 stable is released it'd be good to start on the port for ubercart.

We've been maintaining our d7 ports in launchpad, and its working pretty well. PM me if you want more information about that!