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Sebastian to Aston Martin along Lance Stroll. I would have kept Perez but Lance isn't going anywhere so it seems Perez will leave and go to either Haas and replace Grosjean or Alfa Romeo and replace Raikkonen!
But there's another option least likely but how about this. Sebastian to Mercedes and Bottas to Aston Martin!??
That would be unfortunate for Russell, I really want him to get that Merc seat after Lewis/Bottas leave and as long as Lewis stays, hiring somebody like Vettel who is definitely not going to buckle down for second driver status seems a really unwise decision, while maybe Russell could gain some valuable experience if he comes in after Bottas and gets to race alongside Lewis (will also be more exciting!)
The best IMO would be if agent Toto and Lawrence Stroll buy a share in Williams and as they are improving again now and with the new budget limitations (hopefully) get to move further up the pack, Lance gets to develop further there for a few seasons, while Aston Martin get themselves a well experienced lineup with Seb and Checo to continue their surge. It would be so fun if that happens. As for Alfa Romeo seat, I think if Shwartzman/Schumacher win F2 this year, Ferrari should promote the winner to replace Kimi if he's had it with F1.