Much too early to be asking this question, and... it's kind of a weird question to ask, really. Publishers don't typically just pick up a whole series, then drop it later. No, each game is licensed individually, and VERY RARELY will you ever see a sequel get licensed while the previous game is still being worked on.
The real question you should be asking is, will we localize 3rd? Maybe skip ahead to Sen, since so many fans have been asking about that? Maybe both? Maybe neither?
And in answer to all of those questions, only time will tell. If we release SC and it's a total flop, even on Steam, then... yeah, there's a good chance SC will be the last Trails title we release. If it's even a mild success, though (which I think is almost a given!), I can't see us stopping there.
Basically, as long as there exists interest in the series, we'll continue to pursue titles within it. But probably only one at a time, so until SC is released (or at least READY for release!), we're not going to be able to say much more.