Saying never? I would like that this can be true, but, it always can be a 1% of chance for the opposite scenario
The only times it might be possible for mining to unprofitable for everyone are:
- The price drops enough to cause the difficulty to drop to 1. If the price is low enough such that even mining with a difficulty of 1 is not profitable, then nobody can mine profitably (in general).
- There is enough unprofitable hash power (for whatever reason) that the difficulty is high enough to make it unprofitable of the rest of the miners. Note that this is one way for someone with a lot of money to take over Bitcoin -- cause enough miners to drop out that your share rises to 51%