It depends where he wants to take his career. If he goes the Valverde route, he should be able to get similar GT results as, well, Valverde, while also being (one of) the best in the more hilly classics. For a Tour win, all the stars would need to align though (didn't we say the same about Thomas though?). But he could also win every monument, probably bar Paris-Roubaix, if he doesn't. It's a shame he didn't get to ride Flanders this spring to see where his boundaries are on the cobbles, if he doesn't have it there, he should try for GTs imo.
"Similar" GT results could very well include a Tour de France win though. I mean, Valverde never won the Tour, but I think it would be nonsense to say he couldn't have been capable of doing so had he structured his career differently. Imagine Valverde joining Sky in 2012 or whatever - don't you think he would have had a shot?