I think at this point movie fans would hate it if they replaced Hugh Jackman with some really short guy.
So it may be one of those things that doesn't translate well on the big screen. Especially not for the most popular X-Men character on the big screen who has been portrayed as having pretty much the perfect body for the last 10+years.
I'm sure they will come up with someone pretty unknown, just as they did when Hugh Jackman won the role. No names come to mind for me
(Zac Efron? - NO.)
A little look down memory lane, at who was considered in the past -
Dougray Scott - actually won the role! But was forced to drop out after breaking a limb on the set of MI2 (Thanks, Tom Cruise, for screwing up my chance at super-stardom!)
Seriously considered:
Viggo Mortensen
Aaron Eckhart
Edward Norton