Not sure how informative this is and I don't draw any conclusions. But when visiting Tesla Coral Gables (was thinking about upgrading to X), I had an argument with sales lady who insisted that no matter when I bought my Model S (it's 2017, delivered in September) my supercharger is transferable to the new owner. She was so sure about it, so I just said - you know I can take your word for that, sell it with this promise and when free supercharger does not transfer blame her in this, but she was so sure that I had just to stop that conversation. I knew that if Tesla changed that policy it would be all over the internet, so I believe that sales person had no clue.