...would bitcoin cease to exist...
No, because Bitcoin would remain the chain with the highest hash rate / proof of work.
that's another thing i meant to ask you about... I was wondering how do you figure that? just out of curiosity. for instance if you suddenly have high transaction rates of.. say 10-20 dollars you are going to push a lot of transactions off the chain to something else. Those transactions pay fees too that you no longer would be getting right? (or do I misunderstand?)