#2 "The Demon King" return

There has been an advertisement of WrestleMania 35 that features Finn Bálor in his "Demon King" attire which has begun speculation that his alter-ego will be returning.
This could be the first time Bálor will show up as "Demon King" at WrestleMania, in the past, he has brought out his alter-ego only at Summerslam and TLC pay-per-views.
WWE has still not confirmed that "The Demon" Bálor will be returning at WrestleMania this year, although they might be planning to bring it.
#1 The Four Horsewomen closing the show holding all the women's titles

Last week on SmackDown, Charlotte Flair defeated Asuka for SmackDown Women's Title, it was a really shocking title change just two weeks before WrestleMania 35.
There have been rumours that the reason for title change was to add another stipulation to this match that the whoever gets pinned loses his title.
If this stipulation gets official, we might see all four horsewomen of WWE champions at the end of the WrestleMania 35.
Major rumor about recently released stars HERE