But seriously, I think that Djokovic and Murray (who are at friendly terms) have agreed that only one of them would play Basel. (Otherwise they could meet there already in the semis.)
I agree at the moment it seems most likely that Djokovic doesn't intend to play 5 events in 6 weeks.
Like all of the Big 4 he prefers to play 2 (or 3) weeks prior to and rest the week directly before a Slam. But the WTF is a short and relatively fast tournament. Probably he plans to gather pace at Paris (treat Paris and WTF as one step) while Federer and Murray wouldn't go all out there.
I don't know if there's a friendly agreement between Djokovic and Murray, but it makes sense for other reasons :
- Murray will probably skip Paris as it would have been strange for him to play right before the WTF in his country, it might even have been criticized in his country who will welcome the "hero", that way he can also make promotion in London the week before the WTF. But he needs to play one indoor tournament to get rhythm, and it's Basel, where last year he asked for a wild-card to withdraw in last minute because he had slept badly and had a problem with his neck (to play very well in Bercy next week), which was understandably very badly considered : he kind of had to go to Basel to keep his reputation among tournament directors ;
- for Djokovic, there are more points to gather in the rankings in Bercy for the YE #1 than in Basel-Valencia and they might also be easier to get if, as I think, Fed and Murray don't come in Paris and play in Basel previous week. It would be quite like Toronto for Djokovic. Besides, playing Paris will allow him to get the maximum money from the ATP's bonus pool (Fed will not have that problem if he plays Shanghai as it's a priviledge of his age, and Fed has to play Basel of course).