We've had some discussion of this before, and in descending order from "virtual certainty" it's pretty much assumed we'll get the B-Wing, TIE bomber & Lambda. It's that #4 that's the perplexing issue, since by this time EVERY OT ship that would "work" is accounted for (by this I mean, no, a Corellian Corvette won't work). I've already gone out on a limb and guessed… the Ghtroc light freighter. Yep, the turtleship. WTF, you say? Well….
1. FFG seems to try and maintain balance in their releases. Two rebel, two Imperial; and generally equivalent strength. The B-Wing is a tougher customer than the TIE bomber, so it stands to reason the opposite number of the Lambda should be weaker. Outrider is a little tough.
2. The minis game is not FFG's only Star Wars property; they also have the RPG, Edge of the Empire. One can expect FFG ships will do "double-duty" in the RPG. For Player Characters, they can currently start with one of three ships: a YT-1300 (covered), a Firespray (covered), or… a Ghtroc (NOT covered).
SO, I'm gambling on that long shot!