What will happen once after a fork, every decides to leave/sell out their bitcoin for the forked alt. Whatever the reason, whichever the fork and outcome name, would that be the end of bitcoin? How will the btc value be afterwards?
And how would the miners react to it?
Bitcoin is community-driven, meaning the community decides who will be the Bitcoin. So if ever your scenario happened and everyone abandoned the former chain of Bitcoin and jumps to the new chain then the latter will be the new and real Bitcoin. When this happens, miners will also jump to the new one, not necessarily abandoning the old one. The new Bitcoin will definitely increase in value drastically and the old one will definitely decline heavily.