BTW while we are at it, it would be possible to combine the segwit change with the ability to specify a P2SH address for payout. Are people interested in that? Or should we wait and update once segwit addresses are used?
You are assuming that segwit is going to happen. If it does, I do not see it happening any time soon.
Allowing more payout types is independent of any other change (it could be implemented even on its own). If some other on-chain scaling proposal gains significant traction p2pool will need to be updated to it but currently only segwit is a mature proposal.