There were ~25 Model S Founders car, I'd expect that there would certainly be no more than that when it comes to Xs and probably less (not all the Founders will want a Model X).
Tesla was actively dampening ramp-up expectations at the last ER; yes, Tesla has more manufacturing experience now than in 2012 but ~70% of the parts are still new and there just needs to be one problem with one small part and the whole line will slow. Complex manufacturing ramps are slow and steady and it will be no difference with Model X, even if possibly quicker/smoother than the S ramp.
(My bold in the quote)