Vimeo won’t “go down” anytime soon. It might get worse/more expensive, but it’s not in imminent danger. And it’s also not the only white-label provider around, either.
Would not be surprised to see the two merged into a single service.
It looks like the majority of their business is in employee training portals for megacorps.
One reason Vimeo is a good deal is that they charge for video transcoding by the minute, not by the file size. So you can upload full ProRes 4K movies and it doesn't cost the earth.