I can see FFG doing a cool pre-EP4 expansion that can incorporate all the cool new elements from Rogue one like those dark troopers and Hovertanks we saw in the movie as well as the AT DT walkers, the cadet troopers and some of the inquistor stuff. Also then they can have Rebel agents from different rebel cells and off shoots and all the cool nods from Rebels and Rogue one in one expansion extravaganza!
It's a smart move seeing as the jump forward to TFA would have been 30 years and honestly too big to connect with the current story they have going on.
Who knows, maybe you'll get Gideon as an imperial commander still? Fenn as a storm trooper? Put some backstory to current FFG characters.
The timing will be perfect as well. Announce it this summer after Bespin launches and have it come out just in time to coincide with the Rogue One Movie. They said Q3 for the figures though, which means they would be out before the expansion... I just find it so weird they would release figures that don't fit in the timeline at all. Unless these are going the route of the Wave 4 and get delayed, delayed and delayed some more to coincide or follow the Pre EP4 expansion.