Okay let's handicap all of the options I've seen floating around...
First to fit the bill this needs to be a wrestler who is not contracted in any way currently to Spike or TNA. And, unless they are intentionally swerving us with the silhouette it needs to be someone bald or with hair short enough to pass for bald in "shadow". Having an easily explainable grudge with the company is a plus, but not a requirement as anything could be made up as motive.
With that said, here are the likeliest options(in order):
Low Ki
He fits the look in the video perhaps better than anyone else. He has history with the company, and a motive could easily be created. He fits with Dixie's desire to bring back past X-stars. He is not contracted anywhere and would surely return to TNA if the money was right. He would no doubt upgrade the roster.
What's working against him? He's a reported locker room cancer, and a guy who burns bridges as a pastime. Would the money required to sign him be worth the headache?
D.O.C.
Bald? Check. Currently not contacted to TNA? Check. Logical vendetta? Check. He seems to fit the bill, and TNA clearly didn't get as much out of him as they should have. There is still a lot there to give, and something interesting could easily be set in motion.
What's working against him? This seems rushed and elaborate if DOC ends up being the guy. But not out of the realm of highly possible either. Its easy to imagine talks have continued between the sides, and perhaps with Pritchard out of the way contract negotiations could have leaped forward. Bischoff is reportedly a fan of his, and we have heard that there were plans in the works for his character. It seems not much is stopping him from being the reveal.
Bob Holly
He also strongly fits the look of the man in the video. He recently worked a show for TNA, at a ONO PPV taping earlier in he year. He too is a free agent.
What's working against him? Father time. No clear motives or history with the company. What could he really bring to the current product?
"Scrap Iron" Adam Pearce
Pearce is bald, and along with D.O.C. probably has the most logical vendetta against the company. He was screwed over in his Gutcheck opportunity, despite coming out victorious. He is clearly on the company's radar and isn't signed to TNA or any other promotion. He is a solid veteran hand who could help out any wrestling company, but at this point probably will never really be a star on the national level. He is a former head booker for ROH and could really offer a lot backstage.
What's working against him? From an exposure perspective Pearce probably isn't worthy of this type of hype, and short of Bob Holly he would be perhaps the most disappointing choice given the possibilities. With that said, he's a younger and better worker than Holly and still has something to give. despite it being logical, It's tough to imagine him being the man in this role.
Davey Richards
While not completely bald, Davey's head fits the silhouette. Davey gave an interview a couple months back claiming to be in talks with both the WWE and TNA, and of the two, TNA seems the more likely fit. If TNA wants to show they're serious about finding the best talent and upgrading the roster, then Davey is an excellent choice as he's arguably as good between the ropes as anyone not signed to the "Big 2". Getting Richards instead of seeing him added to the WWE's glut of riches would be huge for TNA, and he would instantly restore credibility to the X-division in the same way that Aries did. Richard's belief that he is the industry's best performer, yet has been overlooked by the larger national promotions could be his reasoning for his "vendetta". He also isn't booked as part of ROH's title tournament, leaving him free to be removed from their story structure after ASE V.
What's working against him? When will Davey be a free agent? He is reportedly done with his contract as of the day of this event, making him perfect to be the August1 reveal, but he is also booked for a tag title match at ROH's All Star Extravaganza V show on 8/3. Did he sign on simply to make that his last appearance? That could explain how he could show up on Impact Thursday without being a contracted TNA/Spike worker. Also Davey claimed he and his American Wolves partner Eddie Edwards were both in discussions. Is it possible Eddie is signing up North without Davey? Or was TNA perhaps not interested in Edwards? There is a lot up in the air about whether Richards is even available to be the guy in this spot.
That's my assessment of the five most likely choices. Personally, if I were guessing, I'd say Low Ki will be the reveal on Impact. He is also in my opinion the best option of the likely choices, so that could be wishful thinking. But given his history with the company I think he could step right in and really do great work and fit with the direction the company should be looking to go following the recent cuts and the success of Dest-X.
Richards would be my second choice, but again, I'm an admitted mark for the guy. Pearce just doesn't seem like a big enough reveal to be worth this kind of mystery, even though he would make a lot of sense. D.O.C. makes perhaps the most sense, and I could definitely get behind it being him. As for Holly? Well, please let it be
anyone but Holly, he would be a huge step back for the current landscape of TNA.