This was discussed over on /r/java when it came out. The tl;dr is that it’s a poorly worded blog post about the OracleJdk (the one you pay and subscribe to). Graal isn’t going anywhere.
https://www.reddit.com/r/java/comments/1niamuc/detaching_gra...
https://www.reddit.com/r/java/comments/1niamuc/detaching_gra...
What could be happening there is that an Oracle customer uses their customer account to get access to a non-free JDK, such as an update that isn't offered on the public website because it's past the free update period.