Paradox has announced a King Arthur Collection that includes all of Neocore's King Arthur content. That includes the main King Arthur: The Role-playing Game, The Saxons and The Druids expansions, and the Knight and Vassals and Legendary Artifacts DLC.
It sounds like a good place to start if you crave more fantasy and role-playing in your Total War gameplay, and never tried out these games. I've yet to play them myself, but I've heard good things about it except that everyone always complains that the archers are overpowered.
There are no pricing details for the King Arthur Collection yet, but it should hit places like retail and GamersGate in May 2011. That also gives you plenty of time to prepare for King Arthur II in Q4, 2011.