People they want to keep will be able to continue WFH if they want. People who are on the margins or destined for the Performance Improvement Camps will have to come in and warm seats if they want to eke out a year or two more of existence.
(1) people who make their bosses look bad are first to go.
(2) next are people who are perceived to cost their bosses time, regardless of whether it's their fault.
(3) after that, it's usually the infanticide cases: i.e., the people who did nothing wrong but haven't been there long enough to establish themselves.
The infanticide is especially ugly, because (a) it means the company is firing people basically at random, and (b) it rapes the shit out of the resumes of the people affected, because they now have <1 year jobs to explain. The reason it happens is that, empirically, most of the people cut in mass stack-rank purges are new members of underperforming teams... who, by inspection, have had the least to do with the team's underperformance.
Underperformance does get people fired, but rarely. It's at least as likely to get someone promoted, because underperformers usually have a career's worth of experience of being shitty, and therefore have developed such political skills they can easily fail up every time.
Not at Google, you can't. Firing someone who's performing abysmally still takes up to 6 months, between all the process and PIPs and paperwork and shit.
At my work at very anti-remote employer, there are so many people who have obtained permanent remote. So I wouldn't be surprised people who Google thinks valuable would get individual arrangements and other who just themselves think they are valuable are in for rude surprise.
That's how tech companies usually do layoffs. Rather than admit they overexpanded and have to cut people (or that they are cannibalizing their own people to boost executive compensation) they blame it on departing workers by increasing the PIP-rape cutoff.
Basically a company's last effort to cover their butts before firing you. If you contest the termination, they can claim they gave you fair warning and a chance to improve.
If you're ever on one, the sensible course of action is to look for another job. You're next on the chopping block.