Djokovic's results this year proves he is good on both slow courts and fast courts.
I mean he won more fast court titles than slow court titles this year so to speak.
Djokovic is fine on faster courts, although the only reason he did better there than slow ones this year is because with Federer's decline and Murray's injury, the Tour was a two man show this year and that other man is Nadal. Murray is a capable slow court player, but with his hopelessness on clay, things are going to need to be sped up to give Djokovic any competition for the best player once Nadal is gone.
No. You definitely cannot change the surfaces like that! And not because of a single player retired.
Supposedly fast surfaces will become fast again when the game becomes way too physical. Wait 10-15 years, people will start complaining for real.
It was before. Because, well not a single player, but a whole generation, retired is why it was slowed down to start- not that the trend hadn't already started due to the prevalence of servebots but Nadal certainly increased it. Federer's only competition was a slow court player, so they made courts slower so he'd have a real competitor who would sell tickets, create a real rivalry. If the same happens in reverse, it will change back. Right now they are okay keeping it super slow because while that's Nadal's home territory, Djokovic is just fine on slow courts, especially slow HC.