If HBK defeated the streak, what will happen at WrestleMania 26?

I would be upset if he lost at Wrestlemania 25 because it would mean The UnderTaker is maybe leaving wrestling.The way Wrestling works a re match would take place at Summer Slam. The lost at Wrestlemania 25 would affect WrestleMania 26 only if the Undertaker retired or cut down his work load.