I do not think that many people will use bitcoin if that happens.
Most people use bitcoin for the convenience and if we are charged 10-20% more then it will no longer be a convenient payment option i guess.
Bitcoin is not meant to send micro transactions and that is how things are going with the current developments, i am not sure whether the vision of satoshi will be like this,but the convenience factor to send micro transaction have to be neglected and we have to start considering bitcoin to store our assets than using it as a currency.