This site is being deprecated.
Please see the official X‑Plane Support page for help.
You can either buy the special Combo Package that we are offering now - a Digital License and Serial Number to X-Plane 10 that will also unlock X-Plane 11 (for free) or you can buy V11 outright when it is released later this year. Here is the X-Plane.com store page for purchases.
It's up to you, but you can purchase X-Plane 10 now here: http://www.x-plane.com/desktop/buy-it/ because it comes with the X-Plane 11 product key, which is right now $59.99. I am not sure what the official selling point will be on release date, which is the only reason I can think of doing it (because it might be cheaper now). Since you already own X-Plane 10, though, it should not make a huge difference at the end of the day. :)
This site is no longer being actively maintained.