They had zones, raids, dungeons and stuff made for OL and NR since Vanilla WoW was going to launch with all three, maybe not as big as they were when they had their own expansions, but a lot more was fleshed out and ready than you would think. They knew from the start once they decided to stay on EK and Kal, that the first two expansions were going to be in OL and NR, they weren't sure which would come first.