They will have ~1.5 years of runway forever, since the Foundation tries to spend away any money it receives to justify pressing increasingly aggressive fundraisers. The site offers the same service as 15 years ago while ingesting 10x more money, none of which goes to the content producers.
More info here:
https://en.wikipedia.org/wiki/User:Guy_Macon/Wikipedia_has_C...
There's been a ton of development in Wikipedia "sister projects", all of which ultimately benefit Wikipedia itself and the free content ecosystem more broadly. It makes no sense to say that "they provide the same thing as 15 years ago".