That happened the same with animal crossing a long time ago and even today it remains the same
https://www.reddit.com/r/nintendo/comments/8aohna
[Some meta description here]
animal-crossing.com
I didn't know about that, though... while this is true, Animal Crossing's news page has actually been fixed, the specific placeholder page is still around but the main news page is normal right now.
Instead Kirby's news page is still all filled with placeholder text last time I checked, even the main news page. Also, partially unrelated but, when that happend to Animal Crossing in 2018, New Horizon was still yet to be announced, though it took another year for even a teaser (after the Isabelle Smash trailer), so even if the works on the page are related to a new announcement, this does not mean that the announcement will be near.
Next year will be the 30th anniversary of the series and there will almost certainly be a new major game within one year from now... they might be working on the site in preparation for the anniversary or something... (it will be during next year's spring so there's a lot of time left still).
There's also the thing that I said earlier about Twitter: for a few months, they keept a post with advertising of the artbook of Kirby Star Allies pinned to the top of the official page, but some days ago they unpinned it. We're getting close to september, and in the last few years, september has been the time for some Kirby spin-offs to be announced: Super Kirby Clash was released at the beginning of september 2019, and Kirby Fighters 2 got released late during September 2020; the marketing of both games on the twitter page lasted for one year each, after that the banner at the top of the page was changed with the one of the newer game and the amount of promotional posts of the previous game decreased consistently. If this is also true for Fighters 2, they will probably stop focusing on the game around september to leave space for something new, that could still be a spin-off but we are not sure.
There's a rumored Kirby 3D title in the work and while most people think that it will be the next mainline title, I can totally see it being the next spin-off announced next month and being an upgrade of Blowout Blast with abilities and more content; it will probably be the game that will fill the space until the anniversary game will actually come out. Speculation, obviously.