This depends on the type of currency that will be used as a measure, if the full payment is in the form of Bitcoin with a fixed amount, then I think this will be a problem, as your own interrogative sentence
~snip~
the main point is that if they hold it as investment for long term they can have huge profits but what if they want to make transaction and buy stuff with it and higher transaction fees became issue for them as workers might not want to pay higher amount in fees only with small amount of Bitcoins.
I think for now the full implementation of salaries in the form of Bitcoin is still too early. Unless done by:
(1) Giving the amount of their salary still calculated with Fiat but paid in Bitcoin, then it is the employee's sole right and responsibility to keep or exchange their Bitcoin salary. This is because the value of the price of necessities in many countries still refers to Fiat, If price volatility occurs, both the company and the employees can harm each other. When the price of Bitcoin goes up, the company has to spend more Fiat to pay employee salaries, and employees make big profits, on the other hand, if the price of Bitcoin when payday drops drastically, then employees will lose because their Fiat needs remain, but get their Fiat from Bitcoin much reduced
(2) Does not violate existing regulations in the country. Most countries still have not fully regulated Bitcoin as a means of payment. Of course, this will be a legal problem if forced to pay salaries using Bitcoin.
(3)There are many merchants and legal who are willing to accept payments in Bitcoin.