My question involves landlord-tenant law in the State of: California

A tenant was properly served with a 60-day notice. The property is being sold. Escrow is scheduled to close 3 days after end of notice period. Current tenant requested to remain and buyer agreed to enter into a lease with the current tenant, but no lease has been executed.

My direct question is that if the landlord agrees to extend the 60-day notice for an additional 3 days does it invalidate the properly served 60-day notice? I have found no information on this topic. Thank you.