If that ever happens bitcoin is begging for somebody to create an alternative currency. So far all the altcoins failed because bitcoin is just to good to be replaced. But at this point there are going to be so many people that can not use bitcoin at all, that you will make the effort to change to another coin.
What will happen is that if bitcoin really has a 1k USD transaction fee the price will be so high that all the old bitcoiners will not care anymore. But it will lock up bitcoin for new people to come in.
Ethereum and Monero haven't "failed" bud. For the rest, the ones that are not money grabs obviously, then yes, the loogic applies that Bitcoin is (so far) too good to be replace.
I don't think we are going to reach $1k transaction fees, but if that ever happens, then Lightning Network is standing ready.