I do believe that the statement was pretty clear.
When Significant/Milestone DLC is released, things that are basically a 1.5 or 2.0 version of the game, then that DLC will need to be purchased to continue to play user created courses.
It's not for all DLC or minor upgrades, but for significant upgrades, which basically move the game forward....like going from TW08 to TW8.5 or TW9.
Just for me personally, I am not affected.
However....
I do believe, in my humble opinion, that this is the wrong approach, for the reasons that others are stating above.
It's like what Mike said about courses, when asked if a user creates a course that will be released as a licensed course, will that user course be prohibited, etc. Mike said that it is then their job to make sure the licensed course is worth purchasing, that they need to do a good enough job.
It's the same with future DLC, just make it worth buying, and the loyal fans here will purchase.
With the described business model, there is risk of alienating some fans.
I don't think the reward is worth the risk.