Look at what happened to Indycar.
F1 could easily fall victim to a breakaway series, loss of popularity, hiding on channels that people don't watch.
For another series to actually overtake F1 as the accepted pinnacle of motorsport would take a pretty extra-ordinary sequence of events, but ultimately if the manufacturers pull out of F1 and immediately club together to bankroll a pirate championship, schedule it to clash with F1 and offer it to the mainstream FTA broadcasters as a cheaper alternative to F1 in which they don't have to share the rights with subscription TV or make do with highlights, why not? If the new championship had Mercedes and Honda and Renault/Infiniti/Red Bull in it, say, why wouldn't the big FTA broadcasters go for it, and drop F1 from their schedules to make room? I don't think it's likely at present, but it's very possible.
The manufacturers would have to subsidise it quite heavily to begin with, of course, and maybe you're right that they wouldn't want to, in which case they would just pull out of F1 and not replace it with another major motorsport programme, and F1 would just struggle on as it is now, losing sponsors and viewers and competitors and struggling more and more to fill the slots on the grid. It will have to fall a very long way in popularity before it gets overtaken by any existing category.
Edited by redreni, 25 March 2015 - 13:34.