Revenues probably won’t drop as much as you think. Remember the State of California is the big pig at the trough when it comes to property tax collections. The city and county get a fairly small portion.
Secondly, Only people who purchased in the last few years will benefit from a reduction. Many of those will not bother to file.
Finally there will be some offset caused by people selling property that was purhased more than five years ago. Even with a drop in values, the large number of properties with very low tax assessments will offset any drops that occur due to re-appraisal requests.