But even if there's no competitor, if you don't update Glest a lot of people will still go (because no new content means that it gets boring over time). They will go slower, but they will.
With the current information I have, the best thing would be to take Glest 3.2.1, put everything from it into GAE (that isn't already in there), stabailize GAE and then release this new stable product as Glest 4.0 (or 3.3 or whatever). And then only continue the work on this one single product.