While I'm positive it's not Soran, it's not a far fetched idea. Soran did initially make it into the Nexus, maybe he still has a bitter "shadow" there. It was shown that you can pop in and out of the Nexus anywhere along the timeline, maybe he went back to his younger self in the new timeline to convince him to seek revenge on Kirk and company. He's established as a nutty obsessive, so he just goes nuts at a younger age.…
I've been swayed by the argument that “John” and not “Harrison” is the key part of the villain’s name here. Specifically, the theory goes that John Harrison is in fact the Johnny to whom Jimmy Kirk shouts at the beginning of Star Trek
(2009). So that means when Bob Orci said the villain was canon, he was right. It’s just us fanboys who assumed it wasn’t from the canon he and J.J. themselves created.