It is eventual, as we don't count the player existing for versus threads.
The thing about IDW Megatron is he has to be pushed to fight in first key, and when he does it if I recall he is mostly melee and, of course, fusion cannon, with Antimatter being a move when pushed hard, however Stealth Bomber doesn't even have Anti-matter, or, if he does, will never use it. So you can use second key just to stay on the safe side. You could even have both Megatrons in if you want, though that'll be all the Transformers characters to be in