Have you heard definitively that Froyo will be ported to the G1?
No. It is correct, by Google's admission at IO, that Froyo is too big to flash to the ROM on the G1. However, as they mentioned, there could be a custom (non-Google) build that removed pieces of Froyo's functionality in order to get it to fit. Not sure why you would want to do that though. It would be like taking the seats out of a Ferrari though, it would be fast, but not much fun to drive.
"Engineering meets art in the parking lot and things explode." -- Garry Peterson, about Survival Research Labs