[/QI just wanted to ask if this means that perhaps that a Beren & Lúthien and The Fall of Gondolin book are to follow? I can't help making that leapUOTE]
Tolkien attempted to write a "new" version of "The
Fall of Gondolin" but he stopped pretty early on-you can find it in "Unfinished
Tales", it is the story about Tuor-C.T, as a result, C.T had to edit a lot of the chapter about the fall of Gondolin the the Silmarillion-I think the drafts he used are found in HoME 11. BoLT contains the original Fall of Gondolin text, it is very old though and in many ways doesn't fit in with Tolkien's post-LoTR Silmarillion.