Pump.io is muuuuch more than just the core, and there are lots of possibilities to explore already, even if the core system isn't improved.
However, that being said, the core system has several important issues that need addressing, and it certainly be great if Evan could find the time to work on it again (maybe if we could get him some decent funding) and/or be able to delegate on other people. Problem for #2 is... who really knows how the internals of a Pump.io server work? =)
There's also the work on W3C's SocialWG to consider. Since plenty of things will need to be adapted to the "common" agreed protocol, I guess it makes sense to wait until there's something solid.