....it should last 10+ years. By that time, I'd expect some phenomenal new tech like in your OP to be available -- and unfortunately MUCH more expensive too! I know that there are newer models now than mine even though it's new. The R410 refrigerant it uses won't be used in the newer ones, though it will remain available for years in order to service older models. I never had gas, mine was always electric.

...the cost should decrease, as all new technology does as it scales up.

...all of these advancements in non-CO2 emitting technology have just begun and will continue to improve (as technology does) and continue to drop in cost as the industry itself, as a whole, scales up to a broader market, for years to come.

Flammable refrigerants such as propane are kept outside the house and installation is much simplified.

I don't need a heat pump that goes down to -28C, -5C would be plenty adequate in our climate.

I'm looking forward to replacing our gas heat with something like this.

...inside a house as I was when we spent a long weekend with friends who had a heat pump. It was winter. They lived in northern Virginia. I felt like I was carved out of ice.

The heat pump would turn off and an undersized (and expensive!) electric resistance heater would kick in.

My great aunt and uncle had one. The only way to keep the house warm was to keep the thermostat set to at least 70F all day and night. The heat pump could not warm a cold house in the morning so you did not turn the thermostat down at night. My great aunt was okay with that.

Modern heat pumps are vastly improved.

currently the US generates 60% of its electricity from nat gas or coal. if more people switched from nat gas for heating to electricity that would require more power plants. assuming that the new plants were 50% fossil fuel burning and 50% renewable how much would co2 emissions drop. (yes i realize that if the new plants were 100% renewable then there no doubt electricity for heating is better but im going to assume the fuel mix for any new plants would be nearly the same as current usage). aslo theres the cost factor. electric heat is much more expensive than nat gas heating

With heat pumps you get many kilowatt hours of heat for every kilowatt hour of electricity consumed -- how much heat depends on the outside temperature. Over an entire heating season modern high efficiency heat pumps will deliver more than 9 kilowatt hours of heat for every kilowatt hour of electricity consumed. In mild climates they'll do even better than that.

Even with an all gas power grid, and accounting for electrical line losses, a modern heat pump will have substantially lower carbon emissions than a gas furnace or water heater. Other air pollutants will be reduced as well. Gas water heaters and furnaces emit all sorts of air pollutants.