134a will go away eventually, of that you can be sure. The GWP of 1500 is pretty severe (1lb of 134a has the same GWP as 3/4 ton of CO2).

When it becomes hard to source, and if the laws don't change in the meanwhile, I will probably convert to HC refrigerants also. But right now, 134a works and at $3/lb, it's hard to beat the price with any HC refrigerant.

But a handful of states have specifically banned HCs for MVACs. Be sure that you know your local laws. Perhaps pressure can be put on them to reverse these bans when the time comes.