It looks like The Rock will be taking an extended leave of absence from WWE following his match at WrestleMania 28. Immediately following WM 28, The Rock will begin filming his movies Fast Six, Pain & Gain and Hercules. This is expected to keep him busy through the remainder of 2012.
As far as what The Rock does for WWE after WrestleMania 28, one source says not to be surprised if his appearances are very few and far between. Vince McMahon said during a conference call several months ago that The Rock had agreed to do multiple pay-per-view events this year, including SummerSlam. However, that is now seeming more and more unlikely.