Sorry for the delayed response. I don't read these often.
The 40->60 upgrade was completed at my home via an OTA update. Payment of $2500 was coordinated through the local Service Center. My understanding is that the upgrade was then triggered by the Tesla Engineering Department at HQ in California. For me there was no coordination with the team that triggered the update. I parked the car, then a few hours later I returned to the car and it was a 60. I suspect it was a very simple "bit switch" within the software.
Also, the total cost was $2500 because there's currently no Sales Tax for EVs in WA.
I'm relatively confident the policy is permanent, so gently advise your local Service Center if they are not yet aware of the option. Many(!) Tesla employees are not even aware that the 40s exist, so some persistence may be required.