Xtranormal itself may be shutting down, but the Emergent Animation Yahoo group is still going strong. The group is a meeting place for users of State Plus, a set of extensions that transform Xtranormal State into a much more versatile program. We're talking new sets, new actors, new motions, all kinds of impressive stuff. You can see some examples of the kind of work State Plus is capable of doing on the Emergent Animation Youtube page.
If your computer has the power to run State Plus (mine doesn't,) you'll still be able to make Xtranormal movies long after Xtranormal itself has shut down.
I did consider trying to continue the series, using State Plus. But in addition to my aforementioned hardware problems, I just feel like the story of Sweetie and Mr. Meany has to end with Xtranormal. They're so much a part of that world, it would feel weird to go on after Xtranormal is gone.