It appears that rumors are saying this book is going to be coming earlier than thought, as the date listed in this bit has the book coming out for pre-orders the last weekend of February. Here is the latest regarding the Endtimes: Archaon
Please remember that these are rumors.
via an anonymous source on Faeit 212
-Last weekend in February for the last Endtimes book
-2 Hardcover books 248pages
First book has picture of Archaon on his fiery steed charging straight at you with flaming sword held to the side
Second book shows the Archaon model in a very similar pose, but with the Steed's head turned slightly towards the right.