I like that word, alliance. It sounds better than replacement, which may be Rory's actual long-term role at Nike—replacing Tiger.
Selfishly, I hope Tiger wins a major, so we can keep talking about his getting to 19. It's an interesting discussion. An actual rivalry between Tiger and Rory would be even more interesting.
I look at everything from the Tour Tempo perspective, and last year Tiger really smoothed out his tempo. I expect him to be what we've seen of late—a multiple winner who contends in majors and occasionally reminds us of what he used to be, a shadow of himself but a shadow who can still scare most of the guys on Tour.
It was disturbing to see the way Tiger could get near the lead and then apparently lose all confidence in his swing and/or putting stroke on the weekend. I just watched a Ryder Cup replay, and in singles Tiger's body was aligned so far left on every putt it's a wonder he made anything. That's not the technically perfect Tiger I'm used to seeing.
I would never say he can't get back to No. 1 or win more majors, but Tiger no longer looks like he can play any shot at any time under major-championship pressure the way he used to. If he needed to hit a low cut to a back-right pin, he'd do it. Now sometimes he doesn't think he can play the shot he wants so he settles for a different one.