On form I'd say he had an excellent shot at 2nd, but i don't think the race will go to plan.
Last year Froome didn't have to work until there was Wiggins, Froome, Nibali, and maybe 2 others depending on the day. This year I think you'll see Porte having to work and work hard as the spanish guys go to work on sky earlier. Porte in the last 3km Porte will pull himself inside out and reach the other favourites for Froome to destroy them, but he'll be fried. I'll say 6th. Froome, Contador, Rodriguez, Valverde, Pinot to finish ahead of him. I'd like include Quintana in that group, but he'll be fried from pulling the group away in the first place.