I have no idea if Wichmann, Donnal or Brown could become their starting center. My guess is one of them could at least be the backup center. In Donnal's case he might need to in order to make the roster. I'm sure discussions about and maybe with those three about a transition are happening. Whether it's starting or backup they should make that move when OTAs start, not in late July.
I do think there are 2-3 starting centers in this draft. Elflein would be great but I'd much rather use the 37th pick at WR, CB or DE. Spend 69 or 112 (or trade up from 112) on a center.