It's SOP for news organizations to have obituaries and death notices prepared for public figures so they'll have something ready when the death happens. That's why, if they don't have something ready, you'll see a brief obit right away, or the next day for print news, with the disclaimer that a full obituary will run the following day.
With Prince Philip, especially, he's 96 years old, so it doesn't matter if he's ill or not, he could just as easily pass from old age. The presence of that item in the Google News feed is likely a mistake.
Either that, or he really could be dying of something.