Ok just to put things in perspective I will put in my own estimates the drivers, their ranks and their situation:
-Vettel – RBR (confirmed)
-Alonso – Ferrari (confirmed)
-Webber – RBR (confirmed)
-Hamilton – McLaren (confirmed)
-Raikkonen – Reports suggest that he is quiet happy in WRC, not coming to F1 anytime soon
-Button – McLaren (confirmed)
-Rosberg – Mercedes (confirmed)
-Massa – Ferrari (confirmed)
-Kubica – Renault (confirmed)
-Sutil – not confirmed
-Kobayashi – Sauber (confirmed)
-Schumacher – Mercedes (confirmed) *Needs to retire
-Barrichello – Williams (confirmed) *Needs to retire
-Piquet Jr. – Reports suggest that he is in talk with HRT to returen to F1, but reports also state that he is quiet happy in NASCAR
-Petrov- Renault (confirmed)
-Hulkenberg – not confirmed
-Heidfeld – not confirmed
-Liuzzi – not confirmed
-Kovalainen – Lotus (confirmed)
-Glock – Virgin (confirmed)
-Trulli – Lotus (confirmed) *Needs to retire
-Buemi – Torro Rosso (confirmed)
-Alquesuari – Torro Rosso (confirmed)
-Perez – Sauber (confirmed)
-Maldonado – Williams (confirmed)
-Bottas – Willaims (confirmed) *test driver
-D’Ambrosio – Virgin (confirmed)
-Guitterez – Sauber (confirmed) *test driver
-Di Resta – Not confirmed
-Bianchi – Ferrari (confirmed) *test driver
-Chandok – Not confirmed
-Yamamoto – Not confirmed
-Klien – Not confirmed
-Ricciardo – Torro Rosso (confirmed) *Test driver
-Karthikyan – HRT (confirmed)
-Razia – Virgin (confirmed) *Test driver
So from this list we can deduce the following available seats:
RBR – test driver
Mclaren – test driver
Mercedes – test driver
Renault – test driver
Force India – driver 1 & 2 + test driver
Lotus – test driver
HRT – driver 2 + test driver
I think that Force India will put all their eggs in a basket and get 2 of Heidfeld, Hulkenberg, or Sutil. They are the only team without a driver and a crop to pick from.