I think this is worth discussing.
I think that Ferrari is F1's main draw, and losing them would hurt F1 in the short term.
Long term, I think F1 would be well served to lose Ferrari. The barrier to entering F1 is just how expensive it is. Ford, BMW, Toyota, Honda... the list of very very rich car companies who feel F1 is too expensive is long. WHY is F1 so expensive? Because Ferrari will spare no expense to win. (And good for Ferrari, why join a sport and then half ass it?) If Ferrari is willing to spend half a billion dollars, then how can you possibly compete without spending half a billion dollars? If you win, like Mercedes, then you can justify it, but if you lose, like Honda, then a lot of shareholders are going to ask if the money is well spent.
Ferrari is the marquee name for F1. It's the name where a casual fan tunes in and says 'I know what a Ferrari is, maybe I'll see if they're any good'. Without that name, there's Mercedes and... maybe Red Bull. McLaren isn't a household name (in Canada at any rate). Force India, Suaber, Williams... nobody is going to watch F1 to see them.
BUT... if Ferrari takes their half billion dollars and goes somewhere else, maybe Mercedes decides they can win with a slashed budget. Maybe RBR evens out their budget with STR to create competition. If Ford can get back into the sport for 200 million, maybe they will, why not BMW, or Porche or Toyota? 500 million is a lot for a sports drink company to pay, but maybe Monster Energy will jump in for less. Maybe Google or Apple or Amazon are willing to put their money behind high tech racing when there's a possibility of the investment paying off. Giving up Ferrari's brand recognition would be tough, but if you can pull in a half dozen brands that people recognize, AND give a chance to Sauber, Williams and Haas to become 'big boys' instead of minnows, it's worth a thought.
So yes, Ferrari is bigger than F1, but F1 can become bigger without Ferrari.