I've thought about this a lot, and have come up with two things.

If he is truely on Voldie's side, he will return to him, but in no way will he be as trusted as he was before, because of the whole Draco/Dumbledore thing. I think that he may even be serverely punished, but not killed.

If he really isn't on Voldie's side, but instead still with the Order, then I think that like Sirius, he will have to go into hiding until the final battle.

There is no way he would dare go back to Hogwarts, whatever side he is on. It is far too risky for him.