Fine, I personally don't see a lot of the connections you do. I guess we'll have to wait for me to be proved right. The fact that the Revived Rogue got turned into the Phantom and is still being playtested and developed further kind of proves that it was never intended for Theros, IMO.
They'd never create 5 UA for a book, and then drop all of them. They'd never playtest 12 subclasses for a setting. My guess is that they planned all along to have 2-4 subclasses in the Theros book, all the others are meant for Xanathar's 2.0.
(They never attached Magic colors to subclasses before. The M:tG setting books don't mention the colors, either.)
The timing could also be due to wanting enough time to playtest all the subclasses for a Xanathar's 2.0.
Edit: (I don't think aberrations are blue in M:tG, so the Aberrant Mind Sorcerer wouldn't be a blue subclass even if they were planning on designing them around magic colors. They're no-color, right? Eldrazi aren't blue, and they're the primary aberrations of M:tG.)