I think it's worth looking into who's currently contracted for which team for next year at the moment.
Ferrari
Fernando Alonso
Kimi Räikkönen
Force India
Nico Hülkenburg
Sergio Pérez
Lotus
Pastor Maldonado
Mercedes
Nico Rosberg
Lewis Hamilton
Red Bull
Daniel Ricciardo
Daniil Kvyat
Toro Rosso
Max Verstappen
Williams
Felipe Massa
Valtteri Bottas
Slots to be filled
Caterham - 2
Lotus - 1
Marussia - 2
McLaren - 2
Sauber - 2
Toro Rosso - 1
So that's ten slots left. Vettel hasn't yet announced where he's going to be moving to for next year, and suspicions are that he'll go to Ferrari. Kimi is apparently going to be leaving F1 when his contract expires at the end of next year, so Vettel would probably replace Alonso. Rumours are that Alonso will take one of the seats at McLaren, which means that either Jenson Button or Kevin Magnussen would have to go, and word is that it'd be Button. It's a tricky one, as Button has previous experience with Honda, and that could be quite attractive to McLaren. However, given that things haven't gone as well for Jenson at McLaren as he would've wanted, he may think it's time to move on. It's possible that Button may well end up at another team, and given that Toro Rosso have a teenager in the shape of Max Verstappen starting next season, I have an inkling that Button might end up there for a year or two to help Verstappen a bit. Then again, there's always the space at Lotus as well. Grosjean, I think, will probably be kept on by Lotus. That now leaves six spaces. Marussia will probably keep Chilton on for another season, and given Bianchi's injuries, I think they'll give Alexander Rossi the second seat at the team. My suspicions are that given Caterham's troubles at the moment, they may not survive beyond the end of this season. This just leaves Sauber. I'm disappointed by Sauber this season, and have a feeling that they may get a completely fresh driver line-up to try and turn things around next year. Their current test drivers are Giedo van der Garde, Simona de Silvestro, and Sergey Sirotkin. It's already been said that de Silvestro won't be racing next year due to a lack of funding, which is a shame, as it'd be good to have a greater female presence on the grid (the last woman to take part in a grand prix weekend before Susie Wolff did for Williams earlier this year was Giovanna Amati back in 1992), so Sauber may have van der Garde and Sirotkin as their line-up for next year, leaving Sutil and Gutiérrez without drives. The latter may be a problem, given the return of the Mexican Grand Prix to the calendar next year. However, with Pérez for Force India, I imagine that it'll be fine.
So, in short, here's my predicted line-up for next year (excluding Caterham for now):
Ferrari
Sebastian Vettel
Kimi Raikkonen
Force India
Nico Hülkenberg
Sergio Pérez
Lotus
Pastor Maldonado
Romain Grosjean
Marussia
Max Chilton
Alexander Rossi
McLaren
Fernando Alonso
Kevin Magnussen
Mercedes
Nico Rosberg
Lewis Hamilton
Red Bull
Daniel Ricciardo
Daniil Kvyat
Sauber
Giedo van der Garde
Sergey Sirotkin
Toro Rosso
Jenson Button
Max Verstappen
Williams
Felipe Massa
Valtteri Bottas
There's also the rumoured entry of Forza Rossa Racing next year - a team with links to Romania, with one of the key people involved being Colin Kolles, who's been involved with Jordan/Midland/Spyker/Force India in the past, and is currently an advisor to Caterham. I've got no idea who they may want for their drivers, but it'll probably be a pair of drivers with plenty of financial backing.