: Yes and no. Tolkien wrote a bit about the 4th age in the Peoples of Middle-earth, I think, and some in the appendices of the LotR. Supposedly some Russian guy wrote a sequel to the LotR, but you'll have to ask Michael about that one, I heard it was pretty bad though.

I remember reading somewhere that J.R.R. Tolkien had considered, or was doing preliminary work, on Forth Age LOTH sequel, but abandoned the project. I think the title had the word "Shadow" in it.