federer is a money whore these days
no love for the game, just $$$$$$$
He has enough money for 100 lifetimes. And as he said himself, he has left so much on the table by denying exho's and so on, it's mindblowing. He keeps playing because he loves tennis, pure and simple.
Btw, of course he wants to play Rio right now but before long he will start falling in the rankings due to decline - and then he will probably hang up his racquet. He does love the sport dearly but he is also fairly proud, plus he has a family now. It's surely not long before he will get tired of life on the tour and settle down in his country.
On a personal note, I'm not sure I even as a fan would want him to play until he's 35. It hurts to see him decline already, but he is still able to play at JesusFed level a few times a year. Soon he won't even be able to do that.