Are we sure that BTC miners will continue to mine after the supply limit is reached.

Satoshi is monetizing the market makers to create the market for him. Once the market is made, he can say, "good bye" to most of the market makers. He won't need them any more.

So when the supply limit is reached, the market will be made. And there will be a huge amount of transactions (if a true market was formed) that only a few miners (potentially one) will earn fees on.

As of now, BTC fees are completely free market (please correct me if I'm wrong). There's no fee setting, which is what we typically see in these types of markets.

In typical monopolies, fees always rise.

As of now, the bigger the transaction, the bigger the fee you’ll need to pay in order to compensate for taking up space inside the block. This is wrong. This should be inverse.