I think I believe the rumors that Vettel is aiming for Merc and if he doesn't get it he'll retire @
The Red One McLaren already signed Ricciardo and Lando is on a longer contract iirc.
If nothing else I am really looking forward to see the new team matchups, we'll get a great measure of all four drivers by the end of next year. I think all four are closer in performance than anyone is expecting.