I mean, "Time" itself appeared in The Vanquishers, it would be appropriate. At first I thought "The Death of Time" would be a good title, but I think it's too similar to "The End of Time".

Perhaps Death Comes to time as a title (or perhaps a loose adaption in which the Doctor dose not die)

Good point.

I think "Time And Time Again" would be a nice title for a regeneration story.

The only other thing we know about the final special is that it will feature the master so the episode might be called the master of time, the time of the master or master time