There is the possibility that I don't understand what people on NMA are doing or planning. I'm a greenhorn, after all, but as I see it:
It might be time for Killap to reanimate himself for The Restoration Project 2.4...
I don't think this is feasible. Eventually, there must be a life after Killap.
Having a project and progress is very important to motivate a community and keep interest alive.
Seeing an important mod becoming dormant while everything else around it tries to move on, can eventually cause everything to slow down.
However, this is difficult on many levels: respect towards someone else's work, risk of splitting the community, matter of competence and commitment, Star Wars Episode One etc.
But eventually there is no way around continuing RP Mod without Killap.
However I would suggest to do it as a new project, like Fallout 2 Deluxe, which is offered as an alternative to RP Mod 2.3.3, but based on it. Should Killap return he can look at it, take from it what he likes and then decide to upgrade RP mod, or not. Normally something like this would split the community, but with Killap being absent it shouldn't be a problem.
But if Killap doesn't return, then the community has to move on, and eventually, phase out RP with another version.
The question would be who to put in charge of such a project?
I guess the veterans of NMA can figure something out among them, but in case it proves difficult, you could actually vote on it. Have a few candidates and NMA users with a certain amount of posts are allowed to vote. This is a bit elitist, but democracy actually works better that way (i.e. when your up for operation it is doctors who discuss how to proceed, not also the janitor, your neighbour and a boy named Timmy).
Voting would also help to legitimate the project (and especially the person in charge of it) and give it a certain level of commitment, importance and seriousness. This may sound a bit too much, but someone stepping up and simply taking it, could be even more awkward.
A committee could work too, and, if reasonable, all interested candidates could agree to form one on their own accord. Which seems to work rather well on NMA, by what I've seen. But it is important to have a project manager. Besides the problem that committees have the tendency to blockade more than they can agree on.
Killap seemed really capable, and having him replaced, makes me feel uncomfortable.
But if all fails, and the project turns out to be horrible, people can vote with their feet and return to RP Mod 2.3.3.
Worst case scenario: some like it and some don't and you split the community in halve. However, there are already alternative versions (like Nevada and Nevada Crazy Edition) and that seems to work fine. So why not have some veterans step up to create a new version of the RP Mod? Just make it optional. And have a fail-safe by keeping Killap's version available.
Anyway, that's my 5 cents on the matter.