I love Matt Smith. One of my favorite Doctors, if not my outright favorite. He has the right amount of charm and, when necessary, gravitas.
I love the mad scientist eccentricity thing he's got going on. XD My kinda guy!
That being said, I've had a few ideas for the next doctor...
1.) The next doctor should be an old geezer, much like the First Doctor. It will contrast greatly with the young Eleventh.
This reminds me of the biggest problem I had with the show. The Time Lords are
nigh immortal, for god's sake! The Doctor is over 900 years old! That might sound like much, but it actually isn't; when you see the previous Master's episode, where he uses the laser screw-driver on the Doctor, I think it was hinted that any incarnation of the Doctor could stay young up until 1000 years, and
only then do the genes begin to decay into old-age.
Yet, so far, the 9th, 10th and 11th Doctors have only been "900 years old" so far. All of them. Don't you think that's a quick death -- as in, dying three times -- in just a span of a hundred years?
That said, you wouldn't need the Doctor to regenerate just to be as old as the "First Doctor". Hiring an older actor look-alike, or just via make-up, could have the same Doctor we know as "being old".
2.) Or perhaps the next doctor could have a different ethnicity. I'm thinking of some kind of African descent - but he'd still need to be a quintessential Brit. For a time I thought that it would be cool to see an American doctor, but I've since change my mind. The only good Doctor is a British one.
Either that, or a woman. And ginger.
Just Saiyan.