I did a quick search across the source in Lucene, and I think the LongParser and DoubleParser are the only two items in the entire source, marked obsoleted for removal in 3.0. There is one other object that is marked Obsolete to be removed in 3.x, but it is still in the 3.0.3 java code.
I'm going to remove the obsolete attributes from those two interfaces listed, because of the differences of java and C# (not .NET), we can't match this API. Specifically, this reason is because even though Java and .NET allow static members and nested types (both static and instance types), it's invalid C# code, since it doesn't support it.
Either way, since we can't conform to the exact API that java does for the FieldCache, it wouldn't be a bad idea to clean it up.