Trion's Rift did do a large purchase a new disk expansion recently, in addition to the nearly continuous downloadable new content/fixes.
I cannot imagine that with a WHOLE world to work from that we will not see expansions to Defiance, never mind that Trion has (somewhere or other) already mentioned the existence of another alien race that got lost on the way to Earth, and that said race will eventually show up.
So yeah I expect to see plenty of quality expansion of one sort or anther here.