The seat isn't that cold yet, but many could be lining up for a chance to take over Mark Webber's car at Red Bull Racing.
Formula One: Who will replace Mark Webber at Red Bull?
The 2007 world champion has impressed since returning in 2012 from his two-year hiatus, winning twice with Lotus, including the Abu Dhabi Grand Prix. The expressionless Finn enjoys a close friendship with Vettel, but would not be enthused by the promotional work expected of Red Bull drivers.
The Australian, 23, has driven for Red Bull's sister team, Toro Rosso, since 2012 and was employed as a development driver beforehand. Ricciardo, with 17 points from 38 races, has performed solidly, if unremarkably, and would continue Red Bull's formula of promoting drivers from within their stable.
Ricciardo's teammate at Toro Rosso is two months older, but has less experience at the top level. With a haul of 29 points from 27 races, his record is more impressive than that of his stablemate, although he has also shown erratic driving at times, resulting in monetary fines and high-exposure shunts.
Paul di Resta
Force India's Scottish driver has a strong relationship with Mercedes, having won races with them in the Deutsche Tourenwagen Masters Championship. Though he has been overlooked for vacant seats at Mercedes-GP and McLaren, he has been linked with Ferrari. However, he does not offer the charisma associated with Red Bull.
The German, 25, moved to Sauber a few months ago, but had previously been strongly linked with Ferrari and McLaren. Hulkenberg has competed in 45 races, scored 90 points and snared pole in Brazil with Williams in 2010. A long shot, but not impossible.