wouldn't this basically be a state operated reverse mortgage? A financial instrument like that available under 62 would be interesting because as it is now it really feels like a "heads I win, tails you lose" situation. Any policy change that lowers prices gets a bunch of people upset about losing value and anything that raises them gets a bunch of people upset about having to pay taxes commensurate with the value they gained.
That said I could see how this would create a mini prop 13 situation where people don't want to move because they would have to eat a big jump in property taxes.
And many jurisdictions it doesn't matter what your house appraises at, because when yours goes up everyone else's goes up, and they allocate the property tax based on the needs (budget) of the community. So if your house was 1% of the total value in the town, it will remain 1% even if it tripled in price.
That said I could see how this would create a mini prop 13 situation where people don't want to move because they would have to eat a big jump in property taxes.