I am of the opinion that he SHOULD.
I feel that moviegoers are just waiting for him to put on some muscle and return as a Reagan-era one-man-army. He sort of did in MM and it was AWSEOME and peolpe loved it (not just Dolphamaniacs).
I think that´s his niche. Of course, he should branch out and try different things, but his "bread and butter" should always be the "undefeatable superhuman".
Steven Seagal stuck to a similar concept and he has therefor (INCREDIBLY) remained a bigger star than Dolph (in peoples eyes) even though he kinda sucks.