As I was re-watching that episode, I remember Ratchet saying "On Cybertron one isn't born into greatness, rather one must earn it" And also when he said " No no Optimus was more like Jack" Was he referring to Orion Pax?
I noticed that too, made it sound like TFA in that Prime is a rank, meaning there's other primes about or that can be made
A rank, but a rank where there "can only be one on Cybertron". The Prime is supposed to lead the people, there's supposed to only be one at a time, but in Exodus, Orion was named a Prime while Sentinel was still alive (albeit they didn't know he was). I'm going to heavily doubt that there's another living Prime that's NOT one of the Original Seven Primes.
That would make sense, since Prime traditionally can mean "first" or "primary", suggesting it's the rank of the "first citizen" or the leader. There could reasonably be other Primes out there - ones lost to the stars and thought gone forever, then rediscovered, Nova / Nemesis Prime / Sentinel Prime style.