so it will collapse, and new stuff will emerge to fill the void... so?
It will still get done, even without ads. The internet has, oddly enough, been the one to prove that to be the rule, not the exception.
My instance is completely ad-free, I might add.
It has (had?) 80% market share in car navigation systems, and makes money by charging car manufacturers for its product:
https://venturebeat.com/2015/08/03/why-3-car-giants-just-bou...
Apple maps is similar: you pay for the phone, and map updates are free. Android could be the same (if google charged for the OS).
Maps isn't fully free; they charge exorbitantly for the API. The freemium model works for e.g. Dropbox and Vimeo without needing to show ads.