They will be getting profit only for the fees of the transactions, it means that the fees will be much more increased than what they are now.
But came on, dont worry about this, the whole blocks and bitcoins are going to be finally mined on 2140, that is more than 120 years from now, we are not even going to be alive to see those incredible fees.
If the lightning network gets implemented, i dont know what is going to happen to fees, that is something that i am not 100% introduced in.