The usual format for these releases in a boxed addon with four blisters with additional troops or characters, and I can't see that changing this year. Following on from their timeline progression releases, I expect we'll have sets themed from Return of the Jedi and then possibly Rogue One. I'd expect the RoTJ set to have reversible board pieces for Deathstar/Imperial base and base Endor/Forest. Rogue One could fill several expansions but I'd expect the tiles in the first to represent Jedha and possibly rocky terrain like Eadu or an Imperial prison world , like the one in which Jyn is being held.
As for which miniatures that we're likely to see, FFG tends to use characters whose fate is already known, i.e. either the character is canonically dead, or the version of the character only represents how they were in a particular era. For example, we only got the Grand Inquisitor once he'd been killed in the Rebels series, and Luke is being released with different stats based on how far down the Jedi path he was. Here's what I think we may see this year:
Jyn Erso, Cassian Andor, K-2SO, Baze Malbus, Chirrut Imwe and Bohdi Rook
Definitely likely if we see a Rogue One set - some these will be blister pack addon heroes.
Possibly as a troops pack, or in the boxed addon. If they are in the latter, then we might see a commander type as a blister.
As above, and given the R1 information book claims these guys are all sergeant grade, then we'd get some interesting mechanics from them as well.
Rebels from the Scariff Assault
Same scenario as the above 2 thoughts, and again with enough named characters (including a non human), we could also see a blister pack commander from these guys.
Ideal blister pack solo figure.
If we have an Endor set, they're likely to be included. With some named ones like Wicket or the Shaman, we have some potential blister pack solo figures too.
Scout Troopers (Jetbikes)
Several of the boxes feature vehicles or larger monsters and the jetbike could easily fit that role for the RoTJ one. Failing that, scout troopers in the same addon could easily provide the Imperial in-box troops additions.
Ghost Crew (Rebels)
While I think these would fit well into IA, I don't think we'll see them while their story is still being told in the TV series, well unless they suffer a demise, or like Luke have some sort of story-line progression in their powers, which Ezra does.
He makes an excellent anti-hero, and he'd fit in well with the game too. I think we may see him simply because he's iconic in the old EU and he'd sell well.
The ones we saw in Rebels before Maul cut them down. I think these could work in a pack like R2 and Threepio, but I get the feeling we won't, as we already have Vader and the Grand Inquisitor, but I remain hopeful!
He's making a comeback in Rebels, so he's a candidate in my view, and also I suspect Obi-Wan will kill him at the end of Season 3, so he fits the original criteria of having a known fate.
Saw and his Partisans
Plenty of odd-ball heroes in this gang from Rogue One, plus Saw is now in Rebels too. I think Saw is likely to feature even if none of the others.
Mandalorian Jet Troopers
These troops have been seen serving the Empire, but are probably too similar to the rebel jet troopers from the latest IA release.