As it stands, both Spur fans and Mav fans would prefer Dallas to be in the #4 spot.
For the Spurs, having Dallas as the 4th seed means:
1. Not having to tangle with an OKC team that has athletic perimeter players in Durant, Westbrook, Harden, Sefolosha and a solid frontcourt featuring Perkins and Ibaka
2. There's a fair chance that Dallas doesn't make it out of the 1st round
3. OKC would make life more difficult for the Lakers
For Dallas, being in # 4 is better because they have no chance against LA - none whatsoever. They have a small chance at beating SA, and the first round is equally difficult for them (Denver or Portland).
It's in both Texas teams' interests for Dallas to tank their remaining games and drop below OKC.