Nope, MS corporate headquarters is still in Redmond.

Of course, if Steve Ballmer was any indication, MS has had way too many drugs on hand since the 80s so this should be nothing new for them.

Microsoft has never had a Seattle office. Though Google does, and ~10 years ago I heard stories from employees there about emails from HR asking employees to refrain from shooting up in the bathrooms...

I also wouldn't be surprised if Amazon abandons theirs in the long-term. They made a conscious decision to not have a bunch of employee amenities in their office in favor of encouraging employees to (eg.) eat lunch at nearby restaurants, and it does them no favors for the streets around their buildings to be full of junkies.