I think he'll end up doing well the first and second Dana White won't want to look like a complete idiot. It'll all depend on who they give him to fight I'm sure he'll get a favorable match up.
I do not see CM Punk showcasing UFC cailber talent or skills YET, but if they feed him some friendly match ups and he does nothing but eat sleep and train then in 2-3 years he can be a potential UFC worthy fighter.