You'd file for an abatement, and have a pretty good case. Most communities do a property revaluation every couple of years. The valuation for all the units is likely to drop quite a bit in the next reval, notwithstanding the higher, older non-auction sale prices.
Intuitively you'd think that if property values are declining, municipalities would take a tax hit. Not so, because as assessments fall, tax rates (expressed as a dollar amount per $1000 of assessed value) go up. So there is a certain equilibrium.
Municipalities aren't in trouble because of property tax declines (a decline that, generally speaking, doesn't exist). They are in trouble because property tax hasn't fully funded municipal services in the 30 years since the adoption of Prop 2 1/2. Historically, state aid ("local aid") made up the difference between property tax revenue and actual municipal costs. Now that the state is broke, it can't cover the gap because it can't fund local aid. So municipalities are in trouble. (And you will see proposals like casino gambling and legalized medical marijuana clinics gain traction on the promise that the municipalities will wet their beaks by tying some of the new revenue streams to a promised increase in local aid.)
Some time ago I posted Toby's theorem of pendulum development, which explains such phenomena as the Liberty Mutual addition and the City Council's comments thereon. A factor I think I omitted (I couldn't find the post) was the role of "new growth" in municipal finance. Municipalities are initially allowed to tax new growth outside the limits of Prop 2 1/2. For at least the first year, it is like free money. This is part of the ineluctable law of economics and self interest that underpins the theorem, factors that cause councillors to say complimentary things about undeserving proposals.
Sorry to digress....