I'm glad that somebody has brought that up, because it is an interesting development. However, I wouldn't put money on Perez definitely ending up at Ferrari, because Ferrari have signed up a number of drivers to their Young Driver Program - remember Jules Bianchi, for example? That is just within GP2 - there are a number of Italian Formula 3 drivers who have been signed to the same driver program (Zampieri and Bortolotti).
Perhaps they are planning on doing what they did with Massa, which is to place him at Sauber and let him sharpen his skills in the midfield, before bringing him into the main team? If Perez were to go to Ferrari, I suspect that he might be a replacement for Massa - after all, Massa has been in F1 for 8 years now, so it is not impossible that he might choose to move on in a few years time. That said, Massa and Alonso are still relatively young (both only 29 - I know that Massa might seem much younger, but he isn't), so realistically they both probably have quite a few years left ahead of them.
Still, I suppose that Ferrari have done this to widen their options for future talent - which also marks a distinct change in the philosophy of Ferrari. After all, traditionally they have gone for experienced drivers, and eschewed the sort of coaching which other teams have engaged in, but now they are seemingly increasingly interested in looking for new up and coming drivers.
)