With Vettel signing up for the 2015 season at RBR, it definitely puts to bed the lengthy-though-inaccurate speculation that he was off to Ferrari for 2014, but it hadn't yet been announced.
So the focus now surely turns to what Webber's going to do next year.
My thoughts are that (despite his situation) he'd be most keen on re-signing with Red Bull, given that they probably give him the best shot at winning races, which surely is the best he can be hoping for at this stage of his career. If RBR are adamant they're going to change the driver mix, do you see Webber retiring or moving elsewhere? Ferrari? Lotus?
I think there are two parts here.
The first one is that Vettel was NEVER going to be at Ferrari while Alonso is there for a long run. Neither of them (SV nor FA) would be interested on that. Also, Alonso's contract (and possibly, carrer?) ends in 2016, so Vettel having his options open to move the year before "and take over the mantle" on the scuderia from a retiring Alonso make sense.
Then, it comes the problem of Webber being approached by Ferrari last year, renewing one year at a time with RBR (but before this, getting multi-year contracts at his different teams); and there is the current "fall of grace" from Mark and the team after Sebastian did what Webber failed to do a handful of times in the past: pass his teammate while his team was instructing him not to do so...
RedBull announced this week that the STR duo needs more time before a judgement can be made, which might read as "not for 2014". So, Webber can choose to stay, or look to move. The only possible top seat other than RBR available would be Ferrari, assuming that Massa continues to underperform as he has been doing in the last couple of races. However, if Felipe goes back to his early-year form, why would Ferrari take away Alonso's loyal wingman for the sake of a proven wildman as Webber? Also, if Ferrari is interested in bringing Seb in the future, would Webber be interested in going there just to have to pair Seb again, or (even worst) being replaced by him?
So, in my opinion, either he accepts RBR way of life, or retires. Can't see any other feasible move for him inside the F1 paddock (unless, of course, he wants to go to a midfield team...)