Let us assume unlimited block size and partial-monopolies. Thus the transaction fee can always be forced higher in order to generate more revenue for the miners.
Price fixing doesn't work because the incentive to break the price-fixing agreement and undercut the other miners becomes immense; the higher a group of miners agree to set the price floor, the greater the incentive to break the agreement. Say the other miners are refusing any transactions with less than $1 in fees. A miner that picks up the myriad 10-, 20-, 50-, 80-, and 90-cent fee transactions that other miners refuse, in addition to all the $1 fee transactions, is going to positively rake it in whenever they find a block.
If we instead assume limited block size, then the Bitcoin foundation will set the transaction fees, not the market.
The market
ultimately determines the blocksize, and every other parameter. The devs, Foundation, etc. only suggest changes. I think it's highly likely the market will be arbitraging all the controversial hard forks on the exchanges, at least after the first one (there might not be time to make the arrangements if the first one is a surprise).