I would assume this means that he is not in great health. Hopefully I'm wrong and he just decided that 85 years or so of hustling for dollars was enough.
At 94, if he had a health concern, I don't think he'd be planning out 7 months for stepping down.
There's video of his announcement.
https://www.cnbc.com/2025/05/03/warren-buffett-to-ask-board-...
On one hand, he doesn't sound that great (in terms of subtle overall health markers in his voice) when he talks.
On the other hand, he's 94 and most people (especially men) don't make it into their 90s, so...