The Beginning of the End of Roger's Reign?

So, I guess the question has to be asked. Are we seeing the beginning of the end? Are Federer's days at the top of tennis numbered. He lost about 7 times last year and the years before that he only lost 3 or 4. He lost for the first time in a hardcourt grand slam in the semis in a very very very long time.

How many more years with Fed at number 1?
How many more slams for Fed?
Who will be the next number 1?