As has been confirmed multiple times this past weekend, TNA Wrestling has "at least three surprises" tentatively planned for Monday's timeslot premiere of iMPACT!.
Of the three surprises, two have technically been confirmed online, although none were clearly communicated to the bulk of TNA's audience.
In any event, the names due to appear are Sting, Rob Van Dam and Jeff Hardy. It is possible that other surprises are planned, but those are the "three" that have been referenced to us over the weekend. Sabu is also rumored but not at all confirmed.
It should also be noted that Hardy recently filmed sit down interviews a few weeks ago for a promotional video produced by TNA.
