To quote Bay, "If it didn't happen onscreen, then it didn't happen". That was his response when the comics and trading cards came up. So for any Bot or Con that wasn't killed onscreen, they can still be alive and brought back. Only ones we saw die: Jazz Hide Ratchet Leadfoot Arcee Elita-One Starscream Shockwave Driller Soundwave Que The Dreads Sentinel Jetfire Sideways Blackout Ravage And a few more Cons ..... Ontop of all that, we learn if a Transformers spark isn't damaged, they can be resurrected. I think we actually learn that in ROTF, when Sam is told to merge the Matrix with Prime's spark. It's then emphasized in AOE that their life force and essence is in their spark. That leaves the resurrection door wide open for those Transformers whose sparks were not blown to smithereens.