Bobby Roode
It's already been said, but Roode reminds me so much of Triple H. He has a great look, is solid as all hell in the ring, can give a great promo and can work VERY well as part of a team. And he's been criminally underutilized in TNA; how he is only a 1 time World Champion is beyond me, and is borderline disgraceful when you have such a talented guy on the roster. He should have held that strap so many more times than he has and were he ever to have ended up in WWE, he could make it as the foil to a man event babyface. At 38 could he possibly still accomplish that? It would have to happen very soon but yeah, I think he's still mor than good enough.
WWE POTENTIAL PROSPECT: World Champion
James Storm
If Roode should be TNA's Triple H, Storm should have been TNA's HBK/Austin. He has that swagger and intensity, is charismatic as all hell and is good in the ring to boot. The same as Roode though; how is he only a one time World Champion? Now, yes, he is there in NXT every so often, but at 38 sadly I think it's a little late in the game for him to quite hit the level of World Champion unless he were to get over VERY fast. Back when he was white hot and feuding with Roode over the title would have been PERFECT timing, but even though he's cooled down somewhat I could easily see him being on the main roster now fighting for the US title.
WWE POTENTIAL PROSPECT: US/IC TITLE HUNT (slim main event potential though)
AJ Styles
You may have guessed by now that I'm not TNA's biggest fan, but I really would like to be. But stuff like what happened with Styles, and the fact that they let him go, baffles me to this day. Best wrestler outside of WWE right now in my (and many others) opinions, and has every tool (yeah, promos are a little weak but he can more than hold his own) to be one of the best in WWE. Same age as Roode and Storm, but in a different league in terms of just how good he is. That lacking on the mic might be a shortcoming, but you'd see him as a main eventer at some point for sure
WWE POTENTIAL PROSPECT: World Champion
Magnus/Nick Aldis
Magnus took a while to get going in TNA but eventually began to look like a star. Well rounded with a good presence and a very good talker, he deserved to be a TNA World Champion (and GFW Global Champion). Nick Aldis could easily be a Jericho/Angle-type in WWE if given the time to develop, where he could flip from midcard to main event almost on command. And at 29, time is way on his side.
WWE POTENTIAL PROSPECT: Upper Midcard
Amazing Red
A bit of a different one here, I know, but someone there's definitely a place for, either as part of a team or on his own. A high flyer will always have a place in WWE, and Red has been regarded as one of the best on the indy scene. He copuld easily fill the role of someone to go out there and get the crowd off their feet.
WWE POTENTIAL PROSPECT: Solid mid card
Samoa Joe
Gosh, dang it. Another person I say 'what were they thinking?' about in regards to him only having ONE TNA World Title reign, Joe is killing it in NXT. While he doesn't quite have the 'superstar look', he bring a uniqueness both in his appearance and his style, making him stand out from the prototypical main eventer. Does that work to his advantage or detriment though? A little of both in my opinion. He will have a great career when he makes the main roster. As anything other than an upper mid carder though? Unlikely, yet not impossible.
WWE POTENTIAL PROSPECT: Upper mid card.
Austin Aries
...yet again, only a 1-time TNA Champion??? Aries is great, and can do most things very well indeed. A little undersized? If there was ever an era where that didn't matter, we are in it. He can fly, be technical and talks like a boss. another Jericho-type upper mid carder here who could easily entertain anyone watching his matches.
WWE POTENTIAL PROSPECT: Upper mid card.
Motor City Machine Guns
There is ALWAYS room for high flyers. And there is ALWAYS room for high flying tag teams. These guys are slick, they work great together AND individually. Both are still fairly young, and are talented enough across the board that they could really accomplish a hell of a lot there. Could either of them main event? Both could if given enough time to show what they can do, in my opinion. But would they? Time would tell.
WWE POTENTIAL PROSPECT: Tag team Champions (team) mid card (slim chance of upper mid card (both as singles) )