In that case, the fee will keep rising until _some_ miner puts it into a block. Mining is decentralized so empty block attacks won't work unless they all collaborate (good luck with that).
To me, it appears more that mining is effectively centralized in an oligopoly of mining pools, and that there's an increasing tendency towards this, compare [1] in this thread.
It doesn't appear so that everyone would be free to setup their self-sustained rigg and frolic on their own with realistic prospects, as the mantra of "decentralized" (as opposed to a structured environment) alleges. At least, not at a scale that would be decisive for the entire network. Meaning, there's that structured aspect and individual miners come second to this.
I guess, as is, there are sufficient incentives against this, as pointed out by the linked comment. Generally speaking, when the economic pressure increases, the pressure to cooperate may increase, as well. Which may turn out both ways. (Meaning: I really don't know, and I'm not sure anyone may know for sure. Sorry for the Socratic anticlimax.) Said paper suggests that there are incentives for colluding against the system while protecting it at the same time.
To me, it appears more that mining is effectively centralized in an oligopoly of mining pools, and that there's an increasing tendency towards this, compare [1] in this thread.
[1] https://news.ycombinator.com/item?id=31796847