#1 The Fiend interferes
It is a known fact that Bray Wyatt's alter ego, The Fiend never forgets those who tormented him in the past. This is the reason why he is challenging John Cena at WrestleMania 36 and since Goldberg does not have much time left as an active Superstar, there is a possibility that WWE books The Fiend to avenge his loss soon.
While the company would love to give Roman Reigns an opportunity to defeat another legendary Superstar fair and square, The Fiend could very well interfere. As WrestleMania is split over two days, WWE could book the former Universal Champion to overcome a challenge from John Cena and then have him cost Goldberg the Universal Championship.
WWE could either book him to help Roman Reigns and later reveal that this was all Bray Wyatt's masterplan to set up a rivalry with The Big Dog or they can have Roman win the title and when Goldberg would be laying in the ring defeated, The Fiend would appear and take him out with the Mandible Claw. Either way, WWE needs to end the rivalry between Wyatt and Goldberg with the Fiend having the last laugh.