What is the profit from MN and how will it change?
Masternodes get 20BSD from each block generated every 200 seconds for 30 years from now.
Only amount of masternodes can change reward per node, for now 50%+ of coins(380~MNs) is locked as masternodes.
If 100% of coins would be locked now, rewards would have been halved. But it wouldn't ever happen because price would grow crazy - provoking MN collaterals transfer back to exchanges.