CachedIntrospectionResults, GenericTypeAwarePropertyDescriptor and BeanUtils consistently avoid synchronization now. This is a little bit risky since we're using our ConcurrentReferenceHashMap in those very hotspot places now, which is why this is not really a candidate for backporting. Let's rather use the 4.1 release candidate phase to have this tested in many scenarios.
As a side effect, through ConcurrentReferenceHashMap, we're using soft references for non-cache-safe bean classes now. Previously, we used weak references even for the CachedIntrospectionResults reference which led to rather aggressive garbage collection effects. We should consider changing that part to soft references in 4.0.6 and 3.2.10 as well, simply storing them in the existing WeakHashMap there.