The question, when does bitcoin become useless for us? when do we dump because the fee will become higher than our holdings?
I think when you can't even move 1 BTC per coin because the fee is higher than 1 BTC, the price must be super high or it will collapse.
I will start to think bitcoin as useless coin only When bitcoin will loss all its miners and there will be not much active nodes for bitcoin. I don't think this gonna happen in near future.
If you receive lots of small amount of bitcoin in several transactions, yes fees can be more than your holding in future. I have also seen few transactions where fees and amount in transactions almost same several times.