Well it is a theory. A dubious one best on wishes and hopes but it is a theory. Read again, BTC miners aren't being greedy it just doesn't make sense to radically expand block sizes. Average fees on paying Bitcoin txs have actually gone down over the last two years. The issue is the large number of free tx and a reluctance on miners to expand block sizes especially for free tx only to have them lose money to higher orphan rates.
Miners actually have very little pricing power. If one miner won't accept a paying tx then another one will and the first just makes less money. With pools it means the first pool is less profitable and miners switch to pools which accept more paying txs.
Yes, it's a theory, but this theory is based on knowing human nature, and human nature has been the same for thousands of years, so it's safe to assume it'll stay the same for a while.
BTC miners aren't being greedy? Yeah, right
They are into mining for a profit or for fun? Some are for fun, I am sure, but most are for profit. I don't want to blame miners here, please don't get me wrong. Users are as greedy as miners. I am just outlining what is most likely to happen next, based on what used to happen previously with other money systems that mankind had invented.
See, you just said it yourself, miners don't want to lose money. Current number of transactions is still too low compared to credit card transactions rates. Just wait for it to increase and you'll see what I mean.
If one miner will accept and process it at a loss, that miner will soon be out of business. Again, just common sense.