Not necessarily. If clean energy in Iceland is cheaper than coal in China and can grow indefinitely, increasing the difficulty may push the Chinese miners out of the market, stopping all coal-using crypto-currency mining.
Clean energy can not grow indefinitely in Iceland, there is only so much water falling so many meters. There may be other methods involving steam and earth warmth that Iceland may be uniquely competitive in, but that is going to require the invention of new technologies and processes.
Not sure why they downvoted this. This is an accurate comment.
"and can grow indefinitely"
It's accurate only given this flawed assumption.
It's accurate if both of its big assumptions are true, which seems unlikely given how inexpensive coal is and the relative levels of corruption and tolerance for environmental damage between China and Iceland.