Exactly. Nadal carries 5000 points with him from clay alone so to be number 1, other players have to be really, really good on hard, do well on clay, and do well on grass. In fact, the only way Federer stayed at number one for so on was because of how extraordinarily well he did in tournament after tournament.
Yup! This is the point I've always been making. As long as Nadal dominates clay he's always going to be the likely #1, given that all he really needs to add is SOLID performances outside of clay - he doesn't even need to win any titles outside of clay. Unless someone puts in JesusFed performances in general, which is never likely.
Realistically, Federer is not regaining #1 if Nadal wins RG. Infact, if Nadal had not sustained that injury last year, Nadal would have probably been on a 100 week run at #1 right as we speak.
Federer isn't getting any younger. The best we can hope for is more Grand Slam wins, which is pretty good in itself. The days at #1 are numbered unless Nadal doesn't win RG and then is booted early from Wimbledon while Federer retains his title.