Attila, I'm sorry you found this impolite. It's not intended that way. It is matter of fact, and while that may be something you don't like, lying to you about the situation would be worse.
We don't have any intentions of going back to spend resources on a dying platform like X-Plane 11. 13% is a small amount of customers to put resources into, and that number will continue to get smaller and smaller as people transition to XP 12. The update will always be available to you and free for X-Plane 12 whenever you decide to make that move.