Here is what Elon said about X delay, quote from transcript below. It makes sense.
"Yes, there’s no question we’re delayed on the Model X, although that’s I wouldn’t say particularly new information. Relative to our earlier forecast, we had to spend a lot more time making sure we got the Model S right, and it took longer to get to some of the international markets and what not. So it just didn’t make sense for us to be focusing on Model X if we didn’t have our Model S house in order. I think we're in pretty good shape on the S front, so our focus is very heavily on the X, and just making sure it's a phenomenal product. And, we expect to be varying production cars roughly Q2 next year.
We'll have the production design articles, I guess beta articles or production-release candidates around the end of this year, but we want to make sure we've got a decent period of validation with those release-candidate vehicles, because the production ramp for Model X will be much greater than for S, so much deeper. So with S we have quite a shallow production ramp, start off real slow and as we encountered issues we were able to correct them without having a large number of cars in production on the roads.
With X it's going to be sharp ramp, which means we really need to make sure that we've properly validated issues and made sure in all temperatures and climates and road types that the car is really solid before ramping up production. Otherwise, we would risk having a recall or a bad customer experience."