How far can this current man utd team go?

They are winning because they have an old and experienced squad(players like Giggs,Scholes, Ferdinand..)mixed with talent (Nani,Rooney,Chicharito..).But,most of their players are aging and we didn't see replacements yet.. So,in your opinion,for how many seasons can their CURRENT squad challenge for trophies (If Ferguson continue to be inactive in transfer windows)