...
Just thinking about the future is all. Seems like if and when mining stops bitcoin goes fully Fiat
I think the problem is that you're imagining miners as this special class of people who all know each other. They aren't. They are more like screenplay writers. Or software engineers. Or farmers. They do what they do because it profits them.
If no one does mining, then bitcoin does not go "fiat", it just stops cold. All of the people who want to use it (enough) would offer higher transaction fees until one of them decides to start mining again, and that one would get rich very quickly (unless others joined in the mining efforts). At today's rate, all miners put together earn at least $504,000 every day. How many people who are earning a share of that would stop mining if they were earning only 1/10th of it? They would be earning an average of $50k per day because there were only 9 other people mining. I would start mining at that point, so your question is extremely hypothetical.