It's been well-documented that WWE officials are interested in having Hulk Hogan appear at WrestleMania 30. Although Hogan is not yet officially signed to a contract, the general feeling is that the WWE Hall of Famer will indeed return to WWE for WrestleMania. However, Hogan is not expected to actually wrestle a match, and there is some talk that at this point he wouldn't even be able to pass a physical in order to be allowed to wrestle.
Former WWE World Champion "The Animal" Dave Batista is also reportedly being talked about backstage.
Rob Van Dam's status for WrestleMania is currently uncertain at best. As of right now nothing is being planned for him, but that could change if/when he comes back before WrestleMania.