To me there's always been two ways of interpreting this song.
The most obvious is that it's a tribute to Keith. The singer is at the stage in his life where he actually realizes that the "love of his live" isn't all the jetset-ladies or the groupies he's been hanging out with up til now, it's the man playing guitar in his band.
To say that Mick Jagger's lyrics always been a bit sexistic would be a rather big understatement. That's why I like to think that the song is about a man that finally realize that women can be something else then sexpartners. So he's not waiting for something he can screw, he's waiting for something he can hang out with.
But knowing anything about Sir Mick tells you that the last alternative is probably out of the question.
Well anyways, a remarkable song that just creates a mood so inviting that you just wanna wrap yourself in it.
To me there's always been two ways of interpreting this song.