6. An Older Doctor
The NuWho generation has always seen the Doctor as a young man. Christopher Eccleston's 9th Doctor is the oldest man to play the role in this current run, and both Tennant and Smith skew significantly younger than any of the actors that played the part in Classic Who. That (admittedly short) trend may be ending soon, though. With the introduction of John Hurt in The Name of the Doctor, we're once again in the realm of the character being physically older than many current fans are used to. Its possible, if improbable, that Hurt could retain the role of the Doctor after the 50th. It is also possible that part of the rational for his casting was to call back to Classic Who, and in doing so gauge audience reaction to a newly-aged iteration of the character.