If it comes out that Lewis is going to the Red team... do you think Bottas will win the wdc? Both Leclerc and max had strong finishes to their season....
I can't see Hamilton going to Ferrari. Mercedes is so well-organized and efficient, why go to a team that can't put it together, even with their budget? The scuderia is the graveyard of champions recently, with both Alonso and Vettel wasting precious years there. Hamilton has nothing left to prove.
At his age, I think he will wisely stay at Mercedes for a few more years (until 2023-2024?) and retire.
As for Bottas, I seriously doubt he could win a WC, even if Hamilton was out of the way. He's a great second driver, a bit like Barrichello was: good guy, good teammate, he can win a few races per season, but to win a WC, you need more.