Rebel aces is slated for 3 quarter so I predict for 4 quarter we will see the first large imperial ship. I believe the fighter that will be included in the expansion will be the tie advance. The tie advance is a lot like the A wing as far as amount of play it sees less Vader. I expect to see a missle delete and a few garage mod options as well.

I'd rather see the scimitar assault bomber in it with maybe a customs frigate,

Yeah, they're probably shooting for a couple Imperial huge ships to be released in December. Maybe one of them will come with a TIE Advanced repaint and new cards. Although I'm really hoping they release a TIE Advanced resculpt in the shape of the "TIE Avenger" (the real TIE Advanced!) instead of just a repaint.