Here's my attempt at futurology.
Mercedes: Hamilton/Rosberg
Neither driver can afford giving away a dominant car (which it should remain dominant for '15), and stay for another year.
McLaren-Honda: Alonso/Button
Button will hang on to a seat for 1 year longer as he'll perform reasonably well next to Alonso. McLaren retain Vandoorne on their payroll as he dominates GP2, and ditch Magnussen (more on both later).
Ferrari: Vettel/Grosjean
Raikkonen is pushed towards retirement after another disappointing season, leaving an open seat. Ferrari's first choice is Bottas but it emerges Mercedes have got an option on him to veto this move. Grosjean gets the seat after a close fight with Hulkenberg and Vergne, thanks to a good season with an improved Lotus.
Red Bull-Renault: Ricciardo/Kvyat
Kvyat doesn't impress much but Verstappen is deemed not ready to take his place yet. Both drivers stay put.
Williams-Mercedes: Bottas/Massa
Williams drop in performance but retain Bottas for another year. Massa also does enough to hang on for a final year, with not many alternatives available on the drivers market. However under Mercedes instructions they give a few FP sessions to Esteban Ocon to train him for a 2017 seat.
Force India-Mercedes: Perez/Hulkenberg
Not much going on here with neither driver able to move up the ladder, and both being easily good enough to retain their seats.
Lotus-Mercedes: Maldonado/Magnussen
Grosjean's Ferrari move opens up a spot, which Lotus cannot afford to give to another paydriver given Maldonado's erratic driving in the other seat. With Ocon no longer under their wings, they sign up McLaren-reject-yet-mildly-promising Kevin Magnussen to hopefully become their lead driver.
Sauber-Honda: Vandoorne/Nasr
I like the idea others have put forward of Sauber becoming Honda's first customer, Honda will want that but there's not really many other teams in the grid who could fit - most having already highly competitive Mercedes engines. Vandoorne comes with the engines, Nasr remains as one of the best bang-for-the-buck paydrivers, with very few others available after the superlicense points system comes into play.
Toro Rosso-Renault: Verstappen/Gasly
Max confirms himself as the next big thing but Red Bull play cautious this time on promoting him to the top team already, after a few rookie season mistakes; Max's laptimes cut Sainz's career very short and the winner of the GP2 DAMS duel gets his seat (I think that's 50/50 between Gasly and Lynn by the way - very difficult to predict right now).
Haas-Ferrari: Gutierrez/Marciello
Haas would ideally get a solid experienced driver and an American driver but neither are really available. Haas gets pretty much the leftovers from Ferrari's pool - they cannot afford Raikkonen's astronomical wages, and decides to go with Gutierrez over Vergne because a Mexican is the next best thing after an American, also because Ferrari needs Vergne more on routine simulator duties. Marciello comes short of impressing much in GP2 again but remains Ferrari's best youngster and gets his chance.