It probably can't be Morris since it was reported on Jan 3 that he hasn't interviewed or visited with programs:
http://www.detroitnews.com/story/sports/college/universit... /
And Zaire isn't deciding until April. So Morris and Zaire are out, then.
We can piece together more clues. If it were Rourke the tweets would have mentioned his name (no reason to be cagey about a guy who has already signed). We also know it's got to be a big name to merit "Christmas came early." Plus, it must be a current junior or senior to make the grad transfer possible. Finally, since it hasn't been made public already, it's likely the QB's team is still playing.
Put all that together and...it can only be Deshaun Watson. When you've eliminated the impossible, whatever remains, however improbable, must be the truth.