Nowitzki has played his entire 16-year career in Dallas, and Mavericks owner Mark Cuban has stayed loyal to him at every turn. There has been no indication of a rebuild on the horizon anytime soon, and Nowitzki hasn't let on that he'll look to leave.
Nowitzki's no-trade clause in his contract ensures he won't go anywhere this season unless he asks to be dealt, which is almost certainly out of the question. Dallas looks like it can contend for a playoff spot at the very least, so it's a safe bet that nothing will change until the offseason.
While you would assume that means he'll be staying in Dallas and bringing a free agent to him, Nowitzki will have options to explore if he so chooses.
Nowitzki is short on time, so the only sensible move other than staying in Dallas would be to join a team with a better shot at the title than the Mavericks. Nowitzki has made plenty of money in his career, and we can reasonably assume that he'll sacrifice a few extra million a year for the perfect fit.
Dallas is the heavy favorite to retain Nowitzki, but the following teams will at least be worth considering should they come after Nowitzki in free agency.