Since Inter Milan isn't in good phase, I think Martinez should stay on there and keep carrying Inter Milan until become a champion at Serie A (at least).
looks like a lot of rich clubs want Martinez. Apart from Manchester United and PSG, there seem to be rumors from Real Madrid that they want to bring Martinez into the squad as a replacement for Benzema.
If Martinez is going to be sold in the winter transfer window, I think a lot of rich clubs have already taken steps to get him.