This is true! But I think the "good" (?) news there is Annapurna Studios is not going anywhere, and they retained all the IP their subsidiary holds.
Sucks for the former Annapurna Interactive folks that they can't bring the IP with them, but c'est la vie.
If they had been laid off, that would be terrible. Choosing to all leave at once is, I'd argue, great! It implies that their integrity as developers trumped whatever corporate bullshit the suit at the top was peddling.
Annapurna will live on under a new name in whatever studio they go on to found. The shell they left behind will likely retain the Annapurna name (as that's the only thing that will give it an air of legitimacy), so we as players will have to decouple the link we'd collectively formed between the name and quality.
I'm excited to see what unnamed studio composed of ex-Annapurna devs does next!