Why?
Seriously, everyone complains about Creative's writing nowadays, and as a suggestion for improvement? Put forward something they would. Kane being involved adds nothing, having taker beaten by a young superstar does the most good for the company, sure it might not draw as large a crowd (which, lets be face it, at mania it will be a huge crowd anyway) but who cares? long term thinking is what's needed is a young'un to win, what bigger push for a career can you have than ending the streak? You have a certified main eventer until they retire. Kane doing it will give Kane a push to being the main eventer where he has largely been a middle carder throughout his time, but how long will it last, 2? 3 maybe years?
This is why taker vs HHH is ridiculous, what possible good can come from HHH doing it? He should be happy with his current cushy role as an advisor/vice president/whatever the hell he is supposed to do. His current participation as a wrestler is doing nothing but harm to his reputation, that said he is competing with Nash, who can't even walk across the ring without tearing his quad, so that at least makes him look a little better than he actually is.
As great as taker has been for the business even he must be seeing that it's time to leave it be, he can only do 2 months max a year by now, most of which is just promos! I'm sure he can respect that he doesn't have it in him anymore, retirement MUST be close, this should, with all due respect (and there is a lot), be his last mania. As mentioned Kane getting the better of him would do no one any good, giving a Barratt, Bryan. Even comeone like Punk would be a big one, should he face taker at Wrestlemania he has cemented his position as THE MAN at the company, and he's still young enough to get a lot from it.
Anyway, I'm hooked to this It Begins stuff, guessing is useless, promos is the thing that WWE are best at nowadays. I'd assume that the girl is metaphorical, maybe mid match in the next Raw the girls face will appear on the titantron and just say "It Begins now", cue entrance of whoever it is (Y2J, Vince or taker being most likely) to destroy whoever is in the ring (or not in Vince's case, which is why I doubt it will be him).