Here is a good quote from Satoshi:
Right. Otherwise we couldn't have a finite limit of 21 million coins, because there would always need to be some minimum reward for generating. In a few decades when the reward gets too small, the transaction fee will become the main compensation for nodes. I'm sure that in 20 years there will either be very large transaction volume or no volume.
Give bitcoin 5 years. Either they will be worth the Moon or 0. It is a binary investment. All or nothing.