So what could be possible for 2017
There are some rumours about Montoya is going to be replaced. For example with Newgarden. But most likely all 4 drivers will stay at least for one more season.
1) Simon Pagenaud
2) Will Power
3) Hélio Castroneves
4) Juan-Pablo Montoya
Newgarden is looking for a better shot, at either Penske or Ganassi. But for the moment it seems there are no places available there. So he is very likely to stay. Perhaps Ed Carpenter will do oval courses again, with the car driven from another driver at the road and street courses. Perhaps with Spencer Pigot again.
5) Josef Newgarden
6) Ed Carpenter / Spencer Pigot
Kanaan is going to get another season with that good run so far. All other drivers are very likely to stay. So I expect no chances there.
7) Scott Dixon
8) Tony Kanaan
9) Charlie Kimball
10) Max Chilton
Sam Schmidt expects both drivers to stay, a third car would be great, but that's not very likely.
11) James Hinchcliffe
12) Mikhail Aleshin
Alexander Rossi wants to be back in Formula One, but beside of Manor there are no chances. And for Manor I don't think he has enough money. So, Rossi should be back with Andretti/Herta again - as the other Andretti drivers as well
13) Carlos Munoz
14) Alexander Rossi
15) Ryan Hunter-Reay
16) Marco Andretti
Rahal Letterman Lanigan
With more money they could expand to a two-car line-up. Ed Jones is a strong contender for that.
17) Graham Rahal
18) Ed Jones
Don't expect a second entry. Bourdais to stay I think.
19) Sébastien Bourdais
I think at least one driver could leave. I expect Sato to stay. New driver could be Harvey.
20) Takuma Sato
21) Jack Harvey
Dale Coyne could be reduce to 1 car for Daly.
22) Conor Daly