if your basing it on moving 1btc... the answer is naturally when it becomes costly to the point of over 1% (so 0.01btc fee) to move it people will lose preferential desire to hold bitcoin.
I disagree. People will see an incentive to hold bitcoin as long as the price keeps going to the moon. If the fee is 0.01 BTC, but the price of 1 BTC is $10,000 with prospects of going $100,000 BTC, then who is the idiot that doesn't want to hold that?
As long as the price keeps going up and the fees allow you to move your wealth when needed, it will have an incentive to be the holder's coin.
If the fee becomes higher than 99% of people's wealth and only billionaires see a point in using it, well that's a problem, everyone else will have dumped and only a few will be using it (and I don't see how it can survive in this state, since barely any transaction volume would be going on for miners to be worth mining)