I think the most serious proposal was eight 3 car teams.
They would be Ferrari, Mclaren, Mercedes, Red Bull, Williams, Lotus, Force India and Sauber. So we would lose Caterham (who are all but dead anyway) Marussia and Toro Rosso. Although given the parlous state of Sauber its quite likely that we’d lose them instead of Toro Rosso
But if it goes this way what’s to stop 4 car teams once Lotus and Force India are skint?
Then Merc pull out because they finally stop winning, Red Bull pull out because the find a better vehicle for their brand.
We then end up with three 6 car teams Ferrari, Williams and Mclaren
Williams and Mclaren then get fed up with Ferrari’s political antics (which were bad enough when there were 10 teams to argue against them) and also leave
So F1 becomes 18 Ferraris