It is also speculated that he burned up the last of his life force in his final attack on Rassilon.
That said, considering that Master has survived a collapsing reality, being shot, being sucked into a black whole, being stucked on an exploding planet, and being burnt alive, it's fair to say that the Master will be back eventually.
- I don't think the implication of "The End of Time" is that he died at all. He just prevented Rassilon from using his weapon as all the Time Lords got sucked back into the time lock surrounding the Time War. All the Time Lords are still alive within the time lock, as we saw before they escaped. So the Master's more than likely alive, but doesn't have an (apparent) way back to the "real" universe/time vortex.