I think "needs adjustment" is reductive. Wikipedia could easily 10x pageviews and article count over the next 20 years. If Wikipedia doesn't grow content, coverage, and quality they could become irrelevant. Thinking donations should just go towards keeping the lights on doesn't sit right with me. An endowment that keeps Wikipedia running forever may very well need to be over $1 billion.

It turns out, the folks who planned out the endowment were very thoughtful. Check out this great read on the motivations, challenges, and plans of the endowment. https://meta.wikimedia.org/wiki/Endowment_Essay

The internet technologies will be also improving, which may be even reducing their operations and maintenance costs (per page click).

And when they will _actually_ need more money, they can always ask.

Yes, but for reducing ops and maintenance costs by using new techs you need people to mamke changes to the system. And it's probably not something volunteers would want to commit to do.