The end of the event (main event) will likely be Ryback/Punk but they don’t want the pay-per-view to end in a DQ or screw job as it would take away from both guys. Officials also do not want to end the show with Sheamus vs. The Big Show since it’s not as big of a draw.
One idea that’s been rumored to have been discussed is having Brock Lesnar come out and cost Ryback the match. The issue there is that it would waste a date with Lesnar and the revenge Triple H is expected to put on Lesnar when he returns. WWE is probably going to come up with multiple ideas for the finish during the next week or so.