We've been working on the prospective plans for SummerSlam and were told the following lineup as of this weekend:
John Cena vs. Ryback vs. Mark Henry in a triple-threat match for the WWE Championship
Brock Lesnar vs. CM Punk
The Undertaker & Kane vs. The Shield
Alberto Del Rio vs. Dolph Ziggler. I would assume this would be for the World Heavyweight Championship but I cannot confirm that as of this writing.
As always, these plans are subject to change but they do give you an idea of where storylines are heading into the August 18, 2013 pay-per-view.