His fate (and that of the time lords) was sort of ambigious at The End Of Time.
One thing I think what could happen is that maybe he will take over Rassilon/Dalton's body. That's practically all the Master did in the 80s and 90s, after all (Take over bodies)....and Dalton could work out as a more traditional master. After all, he's been after Rassilon's stuff before, why not Rassilon himself? Also, the Master as lord president could be an interesting twist, as the Doctor has sort of semi-held the position in the classic series.
One thought I had. The destruction of Gallifrey presumabely happens shortly after the events we saw in End of Time, with the time lock not actually being the destruction. However, the Master is now in the time war's final day, and could possibly alter it's outcome. And the key out of the time lock? The mysterious Time lady. In fact, I could swear as the image starts to blur, it looks like he's grabbing her.
One thing I think what could happen is that maybe he will take over Rassilon/Dalton's body. That's practically all the Master did in the 80s and 90s, after all (Take over bodies)....and Dalton could work out as a more traditional master. After all, he's been after Rassilon's stuff before, why not Rassilon himself? Also, the Master as lord president could be an interesting twist, as the Doctor has sort of semi-held the position in the classic series.
One thought I had. The destruction of Gallifrey presumabely happens shortly after the events we saw in End of Time, with the time lock not actually being the destruction. However, the Master is now in the time war's final day, and could possibly alter it's outcome. And the key out of the time lock? The mysterious Time lady. In fact, I could swear as the image starts to blur, it looks like he's grabbing her.