It takes time for the exam to get updated for the next version. The Java 11 exam came out in March. (So 6 months after Java 11 came out.) The first half of our Java 11 book came out in November 2019. (8 months after the exam came out.) [Originally the 819 was a two part exam]. And we were the first Java 11 cert book to market.
Granted the past is not a predictor of the future. But I would be surprised if either of these events were significantly faster. It's really hard to pass a cert exam without a study guide. So I definitely recommend taking the 819 this summer rather than trying to wait for the Java 17 cert.
Well, it's released now, I have an OCP 11 voucher and I was looking to see if 17 exam is going to be any time soon, but apparently not, enthuware expects it mid-2022, so I guess I'll just prepare for my OCP 11.