Spurs fan here. Just read that article in the mirror.
Zero chance of this happening any time soon. Onomah has huge potential but he hasn't even broken into the Spurs first team picture yet - other than a brief cameo in a low key game. Has all the skill and physical ability. Not unlike Pogba in style (and you seem to be after the original!). But mentally still far from ready. Has a languid air about him and can go missing in games.
So nowhere near ready for a move. And, with respect, City is one of the last clubs that he'll want to go to right now. For obvious reasons, it's not the best place for young players to try to break into the first team picture. By contrast, Spurs is one of the best clubs in that respect currently. Not to mention that he's a London boy and a Spurs fan. Not to mention too, of course, that he is very highly rated at Spurs and that they will have no intention of letting him go.
Who knows.....maybe sometime in the future it could happen. But now? Nope. Just chalk it down to yet more media nonsense.