if the movie makers decided to kill off prime, I'm going with nostalgia and selecting hot rod===RODIMUS PRIME.

Dunno, maybe they can re-imagine hot rod into a luxury sports car (ferrari, masarati??) and re-morph him into a bigger "cybertron form" autobot when the matrix is handed down to him (he then trans scans another "bigger" vehicle to fit his size).

I think in the late cartoon no leader ever came close to Optimus except Rodimus . The matrix of leadership made hot rod mature enough in a short amount of time to fill in for Optimus (I also remember that Hot Rod somewhat found it a heavy burden/responsibility filling in?).

In the end though, Hot Rod pulled it off well (against galvatron) before handing the matrix back to the resurrected Prime. After all, he was the "chosen one" to "light their darkest hour" lol.