Manufactures are allowed to sell any 410a equipment and gas they have in inventory . Any HVAC equipment manufactured in 2025 or later must have R454b or equal. I do not see a reason for "sales", as demand for 410a system will remain high, and supply of 454b units will be low.
"R410a will be around for a long time to come. It has been used in the United States since 1995 and is in a majority of the homes currently. As units need repair, the technicians will still be allowed to fix, repair, and even swap out your condensing unit with R410a units.
After December 31st, 2025, all new systems will be required to be on one of the new refrigerants. If you are only replacing the outdoor unit, you can still replace with an R410a unit if it is available. However if both indoor and outdoor units are being replaced, a new refrigerant system will need to be installed."