Don't take it out of the box, then, if you're looking for a long-term investment. And not all STAR WARS merchandise goes up in price. I own figures and vehicles from ten or fifteen years ago that are worth the same or even less now than they were when they were brand new.
So much of this stuff is produced in enormous quantities that it just isn't going to appreciate much if at all over time. The original 1970s and '80s toys are different because so relative few of them are still in their original packaging...back then most kids opened their movie toys and played with them. But so much of the current market is comprised of stuff that's still in the box or on the blister card that quite a bit of it is practically worthless.
Now, the MTT? Who knows. As a $150 motorized and electronic item that takes up a lot
of shelf space and is specifically tied to one of the least popular of the films I imagine it has a much more limited production run than, say, TIE Fighters or Landspeeders. It might get more valuable as it gets older if the production run was abbreviated, but it's way too early to say for certain. If you get one, leave it sealed in the box. I'm sure I don't need to tell you this, but the minute you crack open the packaging and remove the contents it loses half or more of its value.