True, it could be neither of them. I know Marvel seems to be taking risks and going outside the box with the casting of some roles, some have worked others, not so much.
Apparently, with the upcoming Transformers movie, its rumored to have ties into the new cinematic unvierse they are creating with ROM: The Space Knight, Micronauts, and G.I.Joe. So, it could be possible the Last Knight is in reference to ROM, or the Knights of Cybertron. And, they revealed the big bad villain for Transformers is a returning villain.