What do you mean by "right replacement"? If you're expecting another Steve Jobs you have a long wait coming. Visionaries like that come one a decade at best and the likelihood of such a person gravitating to Apple is far fetched.
I think Apple has already made some very bold moves under Tim's direction that demonstrate he's neither steering the company to disaster nor running it on auto-pilot.
It's easy to say we're due for another revolutionary product launch but I think it's unrealistic to simply assume this sort of thing can be accomplished on a regular schedule.
"Every once in a while a revolutionary product comes along that changes everything. It's very fortunate if you can work on just one of these in your career. Apple's been very fortunate in that it's introduced a few of these." - Steve Jobs introducing first iPhone in 2007