According to F4WOnline.com, the feeling within WWE is that Hulk Hogan will be returning to WWE for some type of involvement in WrestleMania 30. Hogan has not signed a deal with WWE as of this writing, and company officials do not expect him to wrestle at the event, as he likely wouldn't pass medical tests to clear him for in-ring activity, so that would rule out the possibility of him teaming with John Cena at the PPV. It's more likely that Hogan would do a run in and possibly knock out a heel and then cut a promo.
As for Batista, WWE has interest in bringing him back for 'Mania, and there has been talk of working him into the show should he want to return.
As for Rob Van Dam, there are currently no WrestleMania plans for the on-hiatus superstar, but that could change if RVD wants to make a return.