I don't know, I think that Kimi and Vettel could co-exist as teammates. They're friends off track, and if anyone could push the team for an equal status with Vettel it would be Kimi. I think if Webber leaves, realistically Kimi will fill the spot. It will be interesting to see where Webber would go though, I'd say Ferrari because they want a strong number 2, with Massa going to Lotus.
Webber to Ferrari would make sense for him, no doubt. I think he could push Alonso.
Kimi and Seb are friends, but as evident with the way Webber has been treated, no way Kimi would get a fair shake. RB doesn't care that they are friends. They need a #2 who knows he is a #2 and nothing more. " We need you to be in the top 10 consistently and nothing more. This is Seb's team". Just my opinion.