lol trust me, CLAMP is really busy. They're often always having trouble getting chapters out by the due date, but they usually get through it somehow through a lot of time and effort. Think about it; TRC, xxxHolic, AND X? It's hard enough dealing with one story at a time. So be patient and appreciate what their lovely hands are doing.
As for the X ending, well most mangakas start their stories from the end to the beginning. At least, that's how they structure it before sending it off. So I'm sure they'll get around to X later on when they've a chance. They also want to continue Clover if they ever get the opportunity.