Given the size of the CR-90 in game (or at least rough estimates) and the fact that it is 150m long, I doubt that we will see any ships larger than about 200m entering the game. That being said, I'm all for seeing some Imperial ships added over time, but I'm in no rush. And for that matter I imagine FFG isn't either since Imperial players will suddenly want to double the amount of TIE Fighters that they currently own and that creates sales for FFG. I know that I'm trying to work out how I can fit in the purchase of an additional eight TIE fighters to bring me up to 16 and thus 200 points of Academy Pilots to through at my opposition.
In your place I'd hold off until we actually see the Huge ship rules. 16 Academy Pilots is nasty (although not as nasty as 15 Academy Pilots and Howlrunner), but with the really big ships on 0 Agility I'd also worry about players just rushing with 10x Scimitar + Protons, evaporating 90+ points of Corvette on the second round, and then taking a victory lap while the Rebel player tries to figure out how to kill 60 hp of Bombers with nothing but a handful of X-wings left.
And coming at the same problem from another angle, if 16 TIEs turns out to be as close as this game gets to an auto-win, they'd be edging dangerously toward pay-to-win, which as far as I can tell they're deliberately avoiding. So it's at least possible that they'll include some kind of rule that keeps you from running cheap stuff en masse.
The purchase of additional TIE's is more for the larger battles that I would start playing. I'd like to be playing 200-300 points a side and have 1 Huge ship, leaving a decent amount of fighter support as well. So it would be 16 TIE\ln and a bunch of TIE\sa and TIE\int thrown into the bargain.