[Formulahistory]

It looks like the amount of full-time rides will go down to 21, but options for 4 additional rides:

Scott Dixon (Ganassi; Dallara Chevrolet)
Tony Kanaan (Ganassi; Dallara Chevrolet)
Charlie Kimball (Ganassi; Dallara Chevrolet)
Juan-Pablo Montoya (Penske; Dallara Chevrolet)
Will Power (Penske; Dallara Chevrolet)
Hélio Castroneves (Penske; Dallara Chevrolet)
Simon Pagenaud (Penske; Dallara Chevrolet)
Graham Rahal (Rahel Letterman Lanigan; Dallara Honda)
Ryan Hunter-Reay (Andretti; Dallara Honda)
Marco Andretti (Andretti; Dallara Honda)
Carlos Muñoz (Andretti; Dallara Honda)
Josef Newgarden (CFH; Dallara Chevrolet)
Ed Carpenter/Luca Filippi (CFH; Dallara Chevrolet)
Sébastien Bourdais (KVSH; Dallara Chevrolet)
Takuma Sato (Foyt; Dallara Honda)
Jack Hawksworth (Foyt; Dallara Honda)
Gabby Chaves (Herta; Dallara Honda)
James Hinchcliffe (Schmidt Peterson; Dallara Honda)
Mikhail Aleshin (Schmidt Peterson; Dallara Honda)
Tristan Vautier (Dale Coyne; Dallara Honda)
Rodolfo González (Dale Coyne; Dallara Honda)

Possible
Ganassi (Sage Karam? Sebastián Saavedra?)
Rahal Letterman Lanigan (Ryan Briscoe?)
Andretti (Kevin Magnussen? Matthew Brabham?)
KVSH (Ryan Phinny? Stefano Coletti?)