Having myself a plugin in the list mentioned above (https://wordpress.org/plugins/ootb-openstreetmap/), the news seems worrying. Fortunately for me, Mapbox is just an optional Tile Provider, but there was a time that I was considering making it the default.

Since it already required an API key to work, I don’t know if it changes much in my case (and probably for most of the other plugins as well), as it seems similar to how we deal with Google Maps. Unless I am missing something, fo course.