I agree its going to be a challenge for Sri Lanka to get back to where they once were when these great players were playing for them. Its just going to take time as finding talent like they had is hard and when a team loses 3-4 top players its hard to recover from. Australia went through this after a few of their top players retired around the same time and so did India. I think they have a few good players but they still need to mature before we see the best of them.
Srilanka will take a minimum of more 5+ years to get what they had in the previous. If you have a look, only Sangakkara, Mahela and Dilshan was playing good most of the time and they were carrying the whole team but Srilanka lost all 3 of them almost at once. It was a big lose. India has recovered its team since after Sachin, Sehwag gone. In fact, I think India is in better position than then.