If Spain gets to the final in Davis Cup i can see Nadal coming back and play but i don`t think this year he will do both WTF and Davis Cup.
The final would be either indoor HC in Argentina or indoor HC in the Czech Republic. He's not coming back to play best of 5 sets on that. Totally not worth it. It's not clay in Spain.
Don't think he'll play till the Abu Dhabi exo and then Doha 2013. Interview with his best friend today suggested the same - that Nadal is in good spirits, enjoying time with friends and family, playing golf tournaments and knows that this is something he has to do for his longterm career - wants to come back without pain and finally take the time out needed. So far he's always taken temporary measures but not this time.
Think this will overall be a good move. 6 months off tour in total; complete rest and recovery of the tendons; time to work on conditioning; mentally recharge batteries and plan the final part of his career. Yes he'll obviously be rusty when he gets back but there's nothing to be gained from coming back for Asia or the WTF. Sad to have him missing for so long and to have Tipsy in the WTF most likely but if it means having him on the tour for longer overall then it's worth it.