The bookies have stopped taking money on Peter Capaldi (Malcolm Tucker in The Thick of It). Top actor, Dr Who Fan, and has worked with Moffat before. Either that or it's someone you've never heard of.
Tom Baker is hugely popular in the UK and was my generations Doctor. He was however, particularly towards the end of his tenure "difficult". He got mixed up in the Soho Drinking scene with the likes of Jeffrey Bernard and felt that Who was his to write, direct and muck about with. After seven years it became his show and he almost felt he could adlib at will. His autobiography is very enlightening.
that said, the man is a legend and the definitive Doctor.