I think the idea is that if you buy the early adopter version, you can just upgrade to the full version and pay whatever difference in price. There was talk of physics being added later, but one problem I can see is that without an updated executable, it might be tricky to adopt plugins, so it might be something only TGC can contribute to. There will be shader support at least, so we should see some developments there that'll benefit DBPro users as well, I think there's already plans for DBPro map support.
Van-B
It's c**p being the only coder in the village.