There’s a difference between lower baptism numbers (true) and decline in membership (not happened yet).
I agree with Phizzy that the criteria for DFing may change. Unofficially, it already has in my observation, because DFing is nowhere near as common now as it used to be. Back in the 80s and 90s it was a fairly regular occurrence, as was reinstatement. These days it hardly ever seems to happen. Why is that? Maybe people have got more savvy about avoiding getting DFed because of online advice and support. Maybe elders have become more reluctant to resort DFing for various reasons: aware that it looks bad to outsiders, don’t believe in it themselves. I think it’s a combination of these factors.