I agree that some Sci Fi would be nice, but I really support your notion of ancient Skeleton Warriors. The current Army of the Dead is great, but they are more ghostly than undead. Ancient & medeval skeleton warriors, to compliment the Caesar set, would be awesome. Mummy Chariots would be fun, but I'd like to see some Werewolf Warriors & Vampire Warriors also, ala Caesar's Ratmen & Lizardmen. (Hate to keep lauding Caesar, but they did come up with some interesting & supplimental Fantasy sets!)
However, I am NOT ready for Dark Alliance to abandon Tolkien yet. Still way more I want to see; Gondor infantry & cavalry, Rohan infantry at Helm's Deep. Armored Dwarvish infantry& cavalry, more Elves, Dwarves, Orcs & men. Character figures, etc.