So I was talking to one of my FLGS staff yesterday and he was pretty animated about Scum Aces/Rebel Vets. According to him (this is taken with a major grain of salt btw) Scum Aces will be the Starviper & Kihraxz fighter and Rebel Vets will be the E-wing and either the Z95/HWK. Both packs would be out after Wave 9. I'm pretty doubtful as to this being the real line-up/schedule, as FFG doesn't really leak stuff that early. But who knows...
As pure speculation, I don't see this as a bad list for either of the expansions. The Scum gets fixes for the real ships that would make sense in an Ace pack (the Scyk needs fixing, but I don't see it as an ace ship- can be fixed in the first Scum Epic release) while the Rebels hopefully get the fix the E-wing needs to make it more competitive, similar to the TIE Defender. Whether the Z95/HWK need fixing/buffing is kind of an interesting question- what would make either of them better at their given roles as cheap fodder and support ship respectively?