In July 2015 the Environmental Protection Agency announced that the United State would be phasing out 134a across the country. The date that was picked was the year 2020 for total phase out in new vehicles. (2021 model year.) There was one exception made for vehicles being exported out of the country. Exported vehicles will have to be in compliance in the year 2024, or 2025 model year.
Over the next few years expect to see the price of 134a to slowly increase and to begin seeing 1234YF become more and more mainstream throughout the country. You can read more about this in an article I wrote earlier this week by clicking here.