Given that it is unclear who, if anyone, deserves "ownership" of the map in the first place...
...that by now, pretty much everyone knows the contents of the initial credits...
...that the map has been shown to benefit greatly from having many different sources of input...
...that with SC2 coming out and time passing, it's hard to be sure exactly who's going to be around for how long...
...that there are already a great many versions of the map in circulation...
...and that the Temple Siege community has, historically, been willing to make up its own mind about what version to play, instead of automatically preferring whichever is newest, and has at least a significant subset of players who place value on balance and skill-involving gameplay...
...why not change the map to open source status? Sure, maybe some edits will be more successful than others, but if people don't enjoy a particular version, they won't host it, and if they do, well, that's the job done, even though it may not conform to your specific vision. Limiting edits to one person is a risky strategy at best...after all, what if they fail to hand it off once they lose interest (an especially large risk these days)? What if their editing style happens to produce maps that, whatever their "objective" merits, the community doesn't like? Plus, if you're going to choose a successor, you're limited to the small subset of people who you know, or who respond to this thread; both the Temple Siege community nor the SC1 map-making community extend way beyond the boundaries of this website, and for all you know, the person who would produce the best next Temple Siege is someone who will never see this thread and never have a chance...that is, if the project remains on a closed-source basis. All the standard benefits of open-source projects apply: since the best ideas don't always come from the best sources, widening the number of contributors is the best way to ensure continual improvements. It's a big change, and possibly a scary one, but there are good reasons to think that it's the sensible way to go here.
None.