My husband is 6' 6" .... will he fit in the Model X????
He should, but of course you will be able to find out once the car is in galleries and stores. I am 6'3", and I know there that Elon is close to 6, and there are a couple of videos showing him in the car with more than sufficient headroom. Of course everyone is built a little differently, so the headroom may differ even for people of exactly the same height.
If you take a look at the Model X Reveal Video, all the guys who get out of the prototype are at least 6'-0" tall or more. The opened Falcon Wing Doors are taller than them all... by a lot.
Franz von Holzhausen was driving. He is about 6'-3" at least. I think you'll fit fine.
I'm 6'4" and fit in the S fine. (With Pano). X should have 4-6" more headroom, based upon my estimate that the X will be about 8" taller. Don't expect all of that 8" to go to headroom. Some will go to higher seating which will make the X easier to get in/out of.
I found getting into the Model S to be difficult. I'm 6'2" but I'm longer in the torso that most, it was difficult to get my head in under the roof. Once I got in, there was plenty of headroom. I'm expecting the Model X to be much easier to get into and I'm anxiously waiting for a demo to show up at the nearest gallery.