Hell, we don't even know if WWE will still be around by then.
Looking thru the 2008 roster, not many superstars from then remain on the roster. Few are in AEW like Cody, Goldust, Matt Hardy, Jericho and Swagger. Of course not mentioning the nonwrestlers but those don't count. Plus the ones still on the roster like Lashley, Orton(I know he main evented 30, not sure which one else if so), Kofi (who didn't main event during his title match), Dolph, Miz (who has), Morrison, MVP and maybe a few others, most aren't likely to main event a mania except for maybe Lashley this year. But with Roman also in the title picture and the women like Sasha vs Bianca a major draw, its not like before where there wasn't as much competition to end the night. If Brock returns than Lashley vs Lesnar has a great chance of main eventing, one of the nights, hopefully night 2. But thats beyond the point. It goes to show that 13 years from now, anything can happen.
Looking at the women, Sasha and Alexa are in their early 30s, Bianca not much older, Becky too and so is Charlotte. They all would be in their mid to late 40s at that time. Who knows if they would still be able to compete. Rhea Ripley is still young tho and I'm sure some of the other NXT women are also so one of them may have a better chance.
WM would be in 2034. That means someone born in 1990 would be 44 at that time, which is old for WWE standards but much older has main evented a Mania so not impossible. Looking thru this site which I know isn't a complete list,
https://www.iwnerd.com/wwe-birthdays-share-birthday-wwe-star/
It seems that most of the wrestlers born around 1990 or later are women. A few guys in there I'm sure but none that really stand out as main event stars at least not yet. Seems like for the guys they all mostly older. I just found out Damian Priest is in his late 30s and I'm sure there are plenty of others who may seem like they just starting out but have been around for years. Thats cuz WWE been getting most of their talent thru the indies now and those guys are already older and established, plus the ones who already had a lengthy NXT or current roster run. So I think that a woman on the roster has a better chance of main eventing 50 than one of the men, but who knows what may happen. Taker main evented when he was like 50 but of course he had a long and storied career. Looking thru the recent mania main events, only 3 men well technically 4, competed in a main event of a mania when in their mid to late 40s and older. Those men were The Undertaker, Shawn Michaels, and Triple H. Big Show too if you want to count last year but that seems like a fluke. So only elite hall of fame worthy talent have main evented a mania in the last couple of years that have been older. Who has that capability on the current roster? Maybe Roman, maybe Drew, maybe someone else. Who knows but I don't think we've met the mania 50 main eventer yet if its a guys match or at least may not be on the current main roster.
We don't know if it'll be a mens amin event match or a womans one. Hell for all we know it could be a treh with how much popularity and interest they seem to be getting lately.
we are washed goddamn 
rocking another re-released WM 17 tee and complaining about the booking
