Eventually, a subscription-based tier that removes all advertisements completely for those who prefer an entirely ad-free experience.
When I first heard about Kagi, I thought that paying for a search engine was crazy. Now that I've had a few months to think about it, I would absolutely pay for a search engine. It's literally the most useful type of service on the internet, and it'd be a great, user-oriented way of supporting Waterfox. (Plus, every other search engine is enshittifying so freaking fast nowadays.)
Waterfox Search worked well for me this morning. Results were what I was looking for, and were literally no different from DuckDuckGo, Google, or Bing. It does seem to be down right now, though. Hopefully that's because everyone was so eager to try it out. :)