I haven't seen this answered for sure on Pete's site or Twitter account, but everything he keeps saying about theming BB 0.6 to look like Gingerbread logically points to it still being based on Froyo.
Am I the only one who thinks this is kind of ridiculous? What is the point of building BB 0.6 from source if not to use the most up-to-date build of Android? Since it is now confirmed that Gingerbread has more or less the same hardware requirements as Froyo did, what possible reason could there be for sticking with 2.2.1? Certainly the other source-based ROMs will be moving to Gingerbread as soon as possible.
I guess most people's response will be that the next version of BB will be based on GB, but at the rate Pete releases updates we might be looking at Honeycomb by then.