I think when the big three retire he can win a slam. With clowns like Mugic and Dimugtrov as his greatest rivals, its certainly possible.
Definitely. You get in Milos a huge server whose return game percentage keeps improving (consistently around or above 30% since the beginning of 2012).
On top of the serve, he has going for him: a great FH, better movement and ground game, an open mind, a fast learner and youth.
Combine all of that and you are certainly in slam territory, more so than Roddick was for example - and he won a slam.
I'd be terribly surprised - and disappointed - if he doesn't win a slam in the next few years.
However, for the time being, he needs to work on his ability to close out big matches.