Globo is the broadcaster in Brazil, Brazil is a HUGE market for F1 with millions of viewers and Globo is one of the biggest media players in the world. They have power and money.
Globo will not show the races unless there is a Brazilian driver because they'll lose a big part of their casual audience that likes to see the brazilian drivers. Globo is also an excellent partner of FOM and FOM would lose a hell lot of money if they lose this huge market.
You can rest assured that Massa will race next year, or at least Felipe Nasr. They can afford a seat in any team willing to sell it, hell, they can pay for both seats and still make a profit out of it, they never had to do it until today because there was at least one Brazilian Driver in a top team in the past 20-30 years.
FOM and Globo needs at least one brazilian driver. If massa can't get a spot because of his potential, he'll be seated by FOM and Globo somewhere on the grid.