The official roster won't be released until August. The cut off date for Superstars that would be in the game was Wrestlemania 27, so it's a possibility.
So far the following superstars/legends have been officially confirmed to be in the game:
Alberto Del Rio
Ted DiBiase, Jr.
The Honky Tonk Man
The American Dream Dusty Rhodes
The Million Dollar Man Ted DiBiase