Goddamnit I knew you would caveat to that nonsense.
2020 negotiations
Mr Juventus: Hey guys, I'd like to negotiate the terms of our future kit deal, we have Ronaldo now.
Mr Adidas: Ok, nice, but we're going to pay you for the amount of shirts you'll sell from 2022 onwards, his contract ends the same year as our current deal, why should I care?.
Mr Juventus: Because he's Cristiano Ronaldo?.
Mr Adidas: How many shirts will he sell for Juve if he goes to China, the MLS or, god forbid, Inter or Milan?.
Mr Juventus: Oh, don't worry about that, we're still 2 years away from 2022 but we're already planning on giving him an extension.
Mr Adidas: Nice, for how many years?.
Mr Juventus: Wel... he'll be 38 y/o once he ends the current contract, so, as usual, we'll offer him an extra year, and if he keeps delivering, maybe another one when he's already 39.
Mr Adidas: Oh, so you want to negotiatie a new kit deal, 2 years in advance, basing your whole marketing operation on a 38 y/o which may leave before the deal kicks in, or can get to stay a year or two in our future 6 year partnership?.
Mr Juventus: Yeah, what's wrong with that.
Jesus
Best case scenario: Adidas or Nike want to close a larger deal with Juve, so either
A) Adidas renegotiate the whole deal to extend it longer in time by improving the amount they're already paying Juventus. Problem with that? Why would they want to renegotiate a deal that's valid for another 4 years if Juve sign Ronaldo, it would be literally the moment Juve could ask for the bigger numbers (peak of the hype) and nothing assures them Ronaldo will sell 1/4 of the sirts he'll sell this year past 2022, a date at which they're still in control.
B) Nike get anxious and want the Juve kit, anticipating an absurd boom in marketing, putting them at the level of Real, United or Barcelona. So they offer an absurd amount of money because Juve now have Ronaldo, so Juve pay a penalty to cancel the Adidas contract (
Chelsea paid 67M to terminate their 300M/10yr deal with Adidas 6 seasons sooner), so they paid 22% of the original deal back, 40% into the duration, if Juve get the same deal, they'll have to pay around 30M.
Problem with B)? well, they need Nike to up the ante as they can't buy out the contract blindly, they need Adidas to be reasonable, it's easier to be reasonable with Chelsea when they don't have... you know... Cristiano Ronaldo, and leaving Chelsea gave adidas cap and money to pursue a deal with Arsenal, which normally could be a lateral step and at worst, a minor downgrade. Losing Juve + Ronaldo in a single blow doesn't have a lateral step in Italy for Adidas, every other club is a downgrade, and no other player in the world would sell more shirts than Ronaldo this year. There's already millions of people in the world with a PSG shirt and Neymar or Messi and Barcelona, I doubt there's a more than a dozen of "Ronaldo 7, Juventus".