It's either Keith Lee, Jeff Hardy, Samoa Joe, Josh Alexander, Will Ospreay, or Okada. That's my six guesses. If I had to rank them in likelihood...
Hardy/Lee
Alexander
Joe
Ospreay
Okada
I'd lose my damn mind if they got Ospreay or Okada. Those are the only two I think would be worthy of the hype it's getting.
Jeff Hardy would be a big name, but completely uninspiring and really disappointing. I frankly would be quite mad if it was Jeff Hardy. Would be a very WWE like move to do major hype for a 44-year-old signing.
Lee would be a big signing, don't think he is a big enough signing for all the hype it's getting though. He's most certainly worth some hype, however.
Josh Alexander isn't worth much hype at all as far as I'm concerned (even though he is supposed to be pretty good?).
Joe would be warranted all the hype if this was like 5-10 years ago, but he's 42 with not so great injury history in recent years.