isn't the fixed and over time decreasing tokens emission already supposed to take care of it?
why do we need to anticipate the time when miners should sustain theirs activity through fees?
When Satoshi designed Bitcoin he expected most users of it to be able to mine using their own full nodes, receiving block rewards, for a lot longer than actually happened, ASIC farms and mining pools hijacked the reward emission to a certain extent. So people who run full nodes are often not mining and not compensated for handling ever larger blocks. So the idea of higher and higher fees is to force tx volumes lower than what the market and ecosystem would like, purely in the theory that it helps the non-mining nodes with less overhead.
The real solution to this is a combination of several things: node services payment channels (like JR has written about), blockchain pruning, Lightning Network type off-chain services, and IBLT which reduces the block propagation bandwidth requirements.
If all these changes were happening then there would be no pressure to try forcing a (misguided) centrally planned fees-market.