When you think about it, every year on the Tour for Federer is like 50+ milions. I know that at this point he is quite a rich guy but you cant simply close his eyes on this fact when decide when to stop. Unless they start beating him big time and he drops outside top 20(which I dont see it happen for at least 2 more years2015-2016) he can easily remain on Tour. If he somehow want to challenge Connors record for titles and match wins, we could see him even longer until 2018-2019. If he plays another five years, this is like 250milions(even more) in his pocket. By the way, is he a bilionare at this point of his life?
I think both Serena and Roger will be playing into their 50s. Even by then these 2 geriatrics will be getting slapped about and bagelled tournament after tournament, they will both still enjoy joke draws, mysterious W/Os from their opponents plus favoured scheduling playing on the show courts and cooler temperatures.