#4 Double Count-out

It may not be a popular option, but it wouldn't surprise many fans if the WWE went for a double count-out to end this match.
Styles is no stranger to the match ending, with one of his several title matches with Shinsuke Nakamura ending like this last year.
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It's unclear how a double count-out would happen in this straight-up singles match, though knowing both men's fondness for aerial offence, perhaps they could both be on the top turnbuckle, grappling, only to go tumbling onto the outside, leaving the referee no choice but to count them out, with Bryan retaining his title.
This would presumably lead to a fourth match between the two for the title, perhaps at Elimination Chamber, leaving the company time to determine a contender for the WWE Championship at WrestleMania.