Redrobes, Diamond, Robbie and I were just discussing the whole project a bit yesterday.
I think if the motivation and will to continue is here, we will keep this going as long as it keeps running with activity.
We will likely have to make a closing date for new lands, at least new continent sized lands.
But bringing new people in to map other facets of the world - cities and other such things - would be encouraged, by me at least.
The idea being that people may want to dig deeper into their country, its history, beliefs, myths, legends, etc.
I know Diamond and I were each planning to do more with our countries as time went on.
I'd still like to get a decent world map compiled in a reasonable amount of time, but that's just one facet of the whole project.

I wanted to do a map with little story bits on the map as well.
Snippets of historical text about this area or that island.