The stations won't "collapse", but merely the number of them will start declining proportionally to the gas vehicles losing popularity (assuming it actually happens). This way, each of the remaining gas stations will have a greater share of the (decreased) foot trafic, thus still maintaining profitability.
That's not how it works in Norway. A lot of stations are so far from the closest neighbour that they have a quasi-monopoly in their area, and "so far" is a surprisingly low number, according to the hearsay I've heard.
The hearsay also says that they close when they need expensive maintenance, not before.
In remote areas with low population density, the stations are like you say quasi-monopolies, so they can just raise the prices if the foot traffic declines. The closures caused by need for expensive maintenance can be a problem, though.
Raised prices in the coming years are what people expect, and is a reason to get an electric car. The gas stations only have a monopoly among the owners of ICE vehicles, people don't have to stay in that group.
