This will never happen. Never.
Ever read a GSA lease? I have. Lots of them. In my work financing commercial real estate I've financed many buildings leased to a variety of GSA-affiliated users (e.g., Bureau of Land Management, Social Security Administration, the FBI, and DoD). Usually these are mission-critical properties specially constructed to the tenant's need. More importantly, the leases do not contain any cancellation clauses, absent significant casualty (i.e., destruction to the property). The tenant has to keep paying. And the leases are long--15 to 20 years usually. Non-payment of rent is a walk-over in court. Landlords will get paid the full amount owed.
As for property owned by the GSA, other than military bases, parks and national monuments, its not much. Sure, the GSA owns office buildings nationwide, but most of their building occupancy is in leased buildings. In many US cities the market for office space and office buildings is soft. Very few will be interested in buying an old, vacant building designed in a brutalist fashion for a government user, with finish levels not desirable to many other tenants, and built in a manner which often cannot be re-used. That means the market value of such properties is minimal, if not zero (and for obsolete buildings with environmental issues the value can be negative).
Federal employees are being told to return to work. 98% will not take the scam 'buyouts'. Even with marginal staffing cutbacks, employees will have to show up somewhere so old folks will still get their SS checks, the FBI will still need an office where they can store guns and withstand a firefight, and the BLM will still have to roam millions of acres in vehicles that can get them around, serve as fire/rescue vehicles and keep scofflaws like Amon Bundy from grazing their cattle for free.
This will never happen. Never...
