I am waiting for 4 month already, and it really sucks. Especially while reading happy stories from Tesla owners... and Tesla moments... and "oh, it's so good, I will get two"...
But, maybe, just maybe, today is The Day.
PS: I'm waiting for new autopilot hardware...
I have seen rumors that the Model X may have better autopilot hardware than the Model S, but these are based on external sensors seen on mules which I don't think were autopilot hardware. When testing a vehicle, you mount various instruments on the car for specific tests that are never intended for production and would not make any sense on a production vehicle.
If holding out for better autopilot has been the reason you've been waiting, it's probably worth it to wait and see what the early Model X owners say about the Model X autopilot, but don't be surprised if the sensor suite is the same as the Model S. I don't like to be the bearer of bad tidings, but I would scale back your expectations a bit.
The only reason I haven't bought yet is I don't have the money together yet. About the only technology I will want upgraded is the battery and in that area Tesla has made indications that people will be able to upgrade batteries when larger capacities come out. It might be expensive though. I expect the cost of the battery pack will go down once the Gigafactory is running, and the capacity might expand by 30-50% in a short time after production begins. But if I get my finances together before that, I'll buy and think about upgrading the battery down the line if it's a big enough range increase.