I'm not a betting man, but I just don't see anyone willing to up that. Barcelona certainly isn't going to do it if he ends up there, in fact I wouldn't be surprised if he willingly accepts a pay cut. PSG at a stretch maybe. Which PL club would hypothetically even entertain the thought of giving him even a similar amount when the best paid player in the league is supposedly on half of that, and that would be only to match? Big bump would put him in CR territory, say 60 million gross per year.
He has absolutely rinsed Atletico Madrid when he signed the contract, exploiting the fact that he was deemed irreplaceable and that they were willing to pull out all the stops. His leverage is nowhere near that level now, club confirmed that he is leaving, he can hardly backtrack now.
Anyways there would be zero way to confirm any of that, seeing as even this 850K figure is by no means official, unlike in say american sports where everyone's salary is known to the last dollar. Wherever he ends up and whatever figure is deemed to be his new salary it would still be speculation only.