The original appraiser should have taken into consideration that the view could be blocked.
What allowable development is permitted between the subject and the view amenity as of the date of value? Private property owners have the right to develop? Height limits of development are known through zoning and building codes. Look at communities where views are common commodities. There are things known as view and light easements, view corridors, in addition to height limits that government uses to regulate such things.Should appraisers include an assumption or EA in the appraisal report for any home with a view amenity (the old 'Million Dollar View') that the value is based on the view remaining unobstructed?
In addition, regulation do change. For example, the coastal development boundary may be located in one place when a project is developed and moved to another location years down the road.the only way to make sure your view isn't blocked is to buy the oceanfront site.