Seeing as I haven't posted in a while... It's all in my name folks!
Unfortunately there are at least three viewpoints that have to correlate (to an extent) before anyone gets the Red Bull seat:
1) What do Red Bull want to put into Mark's seat?
2) What does Sebastian Vettel want in that seat?
3) Who wants to sit in that seat?
From my perspective, none of the above have black and white answers, for reasons I shall attempt to explain.
Let's look at the first question. Simple logic would dictate you put the fastest known entity into the car that you can afford to pay. As they are Red Bull, they could probably afford to pay anyone if they chose to. But if you could get Fernando or Lewis (I use these names as most forums seem to think Lewis, Fernando and Vettel are on another plane of existence), would you?
History suggests mostly not. F1 team management becomes exceedingly difficult and public when two famously quick and competitive drivers occupy the same team. It usually ends acrimoniously, so would Red Bull want to go down that road? For a company that derives most of its money from marketing, I don't think so. Publicity is publicity, but I doubt Dietrich wants controversy.
So, those two are out (contractually they were out anyway). Button would probably be ideal, as he is fairly rapid without the out and out pace to seriously worry Vettel, but he is thoroughly ensconced at McLaren. Similarly for Felipe; rapid enough without being consistent enough to be a threat, and bedded in at Ferrari. Similarly for Nico; locked down at Mercedes.
Of the rookies, no-one catchies my eye much beyond Bianchi, and he has red backing. This leaves JEV, Danny boy, Pastor Maldonado, Nico H, Romain G, Sergio P, the Force Indias and Kimi. I'm going to label those from least to most likely (IMO):
Pastor Maldonado - rapid, but dangerous, and regularly bins the car for no good reason.
Sergio Perez - poor qualifier, reasonably rapid racer. Slightly inconsistent; tied to McLaren (not that contracts have never been broken before).
Romain Grosjean - quick, but inconsistent in the vein of Pastor. If he had challenge Kimi more frequently this year I would rate him higher.
Adrian Sutil - quick and consistent. I rate his chances lower than Nico H or Paul Di Resta as he comes with baggage (conviction and age).
Paul Di Resta - quick, but I don't get the impression he is a future World champion. Could be an ideal number 2 to Vettel.
Nico Hulkenberg - quick, consistent, young. Could be a future champion IMO.
Daniel Ricciardo - has given the impression of being quicker than JEV without scoring more points. Recently he has been trounced by JEV. I don't rate him, but as he is in their program, so I consider he has an inside track of sorts.
JEV - seems to be getting more rapid. I don't specifically consider him to be better than any of the others on this list, but the inside track gives him is in his favour.
Kimi - from an equity perspective it is a no-brainer. I may be biased, but I believe he is categorically faster than anyone else on this list, and he isn't expensive either.
There are a few issues with Kimi though. Is he motivated, is he willing to be part of the team (do PR etc...), and what if he is too quick? When motivated, I really can't put much distance between Alonso, Hamilton or Kimi in spite of the fanboys howling about how he was beaten by Massa.
Now to the second question. I really do not believe that Sebastian will be bothered by anyone on this list, with the exception of Kimi. Sebastian would be deluded (or naive) to consider himself categorically faster than someone of Kimi's pedigree, and he would really need to consider how he would feel to be challenged by a potentially-faster-than-Mark-Webber driver. Lots of past champions have vetoed, or attempted to, the arrival of fast pretenders to their thrones, so he really wouldn't be all that different if he chose to veto Kimi. He also has a very good relationship with Kimi, something he might not want to jeopardise. Selfishness would dictate Vettel would prefer someone other than Kimi.
And who wants the seat? My guess is, if the regulations were completely static for next year, everyone would want the seat. If there were no strings attached, no contracts, etc... most of the drivers would love to have a go in that car.
But the regulations are changing. Red Bull is not a lock for the quickest car next year. Likely as not it will be quick, but I couldn't see any highly paid, contracted driver giving up their security. None of the drivers are in that position though. So, of the drivers that are eligible, I reckon all would definitely say yes to the drive; apart from Kimi.
Lotus has done good things for Kimi. He has the freedom he needs, and a decent car. If the car were more rapid he would probably stay.
So, to my mind the best logical choice is Kimi Raikkonen. From a team perspective he provides the best bang for buck. He is experienced, he is apolitical, he gets on with the principle requirement of driving fast, and he has a good relationship with Seb. Might he be too rapid for Seb's comfort? Yes, but that is the type of problem most constructor's would be willing to cope with if they are winning championships.
Seb might not like the idea too much, but at the same time whoever he faces next is a step into the unknown. He should trust his abilities.
Pretty much the only universe in which I do not see Kimi going to Red Bull next year is the universe in which Kimi says no. I hope I am not living in that universe.