Who's to say that the Timelords are killed off.

Well, Russell T Davies has destroyed Gallifrey, described the Doctor as 'the last of the Time Lords', had him say that his people are gone on numerous occasions and, when Rose pointed out that the survival of a Dalek might mean some of his people survived, had him say that he'd be able to feel it in his mind if there were other Time Lords in the Universe.

All of which leads one to the sensible conclusion that Russell T Davies intends that the Time Lords are well and truly gone for this new series, so one suspects that as long as he produces the show there will be no Time Lords.