These come from an annonymous source who attended the US Games Day and no doubt grilled a designer or two for some info. Here are some rumoured release dates for the new Fantasy Army Books:
Empire - Autumn 2000
Orcs - Christmas 2000
Vampire Counts - Early 2001
Dwarves - Spring 2001
Dark Elves - Early Summer 2001
High Elves - Late Summer 2001
Note that these may or may not apply to the UK.