As noted, unnamed sources are saying Leclerc has a two-year contract offer from Ferrari though Sky was also speculating he might move from Sauber to Haas for another year of "seasoning" before moving on to the Scuderia.
If Charles does go to Ferrari, I don't see Kimi going to McLaren. If Alonso can't succeed in that car, Kimi sure as heck is not and McLaren is going to demand he put in effort developing the car which no longer seems to be Kimi's interest. His WRC campaign was lackluster, but if he does decide to stay in racing, it will be WRC I imagine.
Daniel's options are stay at RBR or go to McLaren. Which isn't really an option since RBR is a heck of a lot better. And even if Team Management loves Max, Daniel has the performance to keep the team staff around him so no real worries of him being "Webbered".
I think Bottas is safe at Mercedes. He is a solid #2 who brings in the points to secure WCCs and he can win when Lewis is off-form. Ocon has shown brilliance, but he has also shown silliness. I don't think Wolf nor Lewis would want him. And Lauda said this weekend that Lewis and Bottas will be back for 2019.