The KDW is still available. I'm not sure if they are making more or just selling through inventory. The Rival is a more aggressive tire with higher available grip and a lower treadwear rating.
I think they're just selling through KDW inventory. The Sport Comp II has taken over a lot of the KDW sizes, but if you go wider like 315/335 and such, the Rival is all that's going to be available in the BFG line.