The Mirrorball Man wrote:
Why would he say they're all dead, if they really aren't, but, actually Time Locked instead? Why would he say he destroyed them all or killed them all, when he really didn't?
For all intents and purpose, they're dead. They're gone, they can't be reached, the Doctor will never see them, they're caught in a loop and will never do anything productive ever again.
Whether you like it or not, the writers' clear intent is that the Doctor is the last of his kind, not that there are lots of Time Lords out there and that only those who were on Gallifrey during the Time War vanished. Otherwise the whole thing has no dramatic weight.
OK, let me clarify my position on a couple of things:
1. I do not believe there are lots of them running around. We know TARDISes were tightly regulated, and running around the Universe freely was frowned upon while Time Lord Society was existent. So, there wouldn't be that many running around in the first place. And, many of those who were running around the Universe freely would have rushed straight home to join the fight. Someone like the Rani (or The Master if he wasn't enticed by the promise of more Regenerations), would've stayed out of it, and could still be out there.
2. Time-Locked is not dead, it's frozen in a moment of time, or outside of time or whatever, and they've already escaped from it once, and Daleks have escaped from it, so, although an almost inescapable prison, it's not actually DEAD.
3. Yes, I realize the Writers' intent is to remove them from the playing field, but, it's not necessarily a permanent situation, there is a loop hole if they choose to use it. If they really, really wanted them dead, they would have been killed, the planet would've blown up, instead of Time Locked. RTD chose to Time-Lock them instead of killing them, so, they could be played with as in The End of Time (Plus The Master and the Daleks returning)