The ending of Cobra Kai doesn't seem to lead into the new Karate Kid movie and Johnny isn't supposed to be involved, so will the characters and events of Cobra Kai even be referenced or acknowledged in Karate Kid: Legends?
Apparently this takes place three years after the events of Cobra Kai Season 6. Given how apparently Mr Han knew Miyagi, I guess he could give Daniel answers about what happened at the Sekai Taikai. I suppose we may get cameos from Amanda, Sam, Anthony & Johnny.
Apparently she was asked to cameo in Cobra Kai and declined. She seemingly hated the production of NKK and let's be honest it's not a career defining role for her as it was Macchio, Zabka,Kove etc.
Unless they retcon his illness in Cobra Kai and explain he managed to get off the boat in time doubt it. It comes out in Season 6 that he has a terminal illness, hence all his talk of legacy etc.
If they still canon to the show, which seemingly as far as I know they intend to, best case scenario is he appears in a nightmare sequence.
I could imagine Terry rising out of the explosion revealing that he survived. I would like to see the villain from The Next Karate Kid return to get revenge against Miyagi Do for ruining his student security guard program 30 years ago.
Even if he did get off the boat, he has a terminal illness and has about 6 months to live, it shows you Terry having a flashback when he is himself, so he was honest when he told Daniel/Johnny he didn't have long left.
This movie takes place three years after Season 6, so in reality Silver would be dead either way.