So far, Tolkien's work has held up for 50-plus years, so it may well attain "classic" status in the long run. This might be because he was a master storyteller, as well a much better wordsmith than Rowling is. His works have depths which reach back into his extensive knowledge of Norse and Teutonic mythology, Christian theology, and European languages.
Whether Rowling's output has the sort of richness that Tolkien's evidently has is up for question. I certainly have not seen it. As to Harry Potter becoming a classic, well, for that it's too soon to tell.
You ain't tryin' to bring reason to this thread, are yuh???
Concur that it is too early; however, there is little dispute that the books are popular in much the same way as Charles Dickens' were in his time. JK Rowling describes herself as "Christain" in practically everything I've read about her. She is a member, I believe, of the Church of Scotland (Presbyterian).
Wasn’t Tolkien’s work condemned the same way as Rowling’s back when he first stated, also?