The Heat and Celtics play again before the end of the season. Winner of that may get the seed advantage, though the Celtics are in tail-spin mode right now. Other than the Boston game, the only tough game that the Heat have is maybe against Atlanta, if they get out of their current funk by then.
I doubt the Bulls lose 3 more though (which would give the Heat the #1 seed if they win out, which seems possible). They could lose vs. Boston, @ ORL, @ NYK, but I doubt they lose all three, and the rest of their games they will be heavily favored.
I don't think the Heat or Celtics really care much about HCA. I think it would mean a lot more to the Bulls.