Ah, well, there are two parts to that. The first part is -- I've never yet seen any volunteer organization that couldn't find more work to do than people willing to do it. And the ODP is no different -- if we had more volunteers who were willing to do what ODP editors do (which is ... find work for themselves to do(!), that is, find websites, review and categorize them), then more ODP editing would be done.
But "needs"? No, not really: it has done what it has done without any more volunteers than it had, and what it does it does better than anyone else around.
As for the time between site submittal and site review for any particular site: there is no connection between that and any ODP need.