What developers used to be able to build 2 units on a 25x100 they can now build 3, allowing them to offer more for 25x100 lots and profit more off these builds. Developers have just started raising offers since the rezoning, so getting one of those properties sooner rather than later will be great, because by the time you want to sell the market will tell you what developers are willing to pay.
The value of the lot is what a developer is willing to pay which they work backwards from resale potential. Look at new construction triplex/duplex condo sales in the heights areas, subtract carrying cost over build timeline, materials, labor and construction costs, what their desired profit in heights deals would be and that would leave you with approximate acquisition cost of the lot.
A much easier way would be talking with a builder/developer, or realtor that represents them like myself, who could just tell you what this value is. Connect with me anytime, i'd be happy to talk further