The difficulty isn't the new release cadence but upgrading beyond Java 9. It's not as scary as it sounds, and even large complex projects can be upgraded within hours to a couple of weeks. For most projects it's a matter of upgrading dependencies (possibly adding dependencies that have been split off of the JDK) and fixing the command line. I would say that the main barrier is if a dependency does not yet work with 9+. Most popular Java libraries do support 9+, but some don't yet and will soon (e.g. Spark).
Once you're past 9, it's smooth(ish) sailing. The new feature releases are somewhere between the old update releases and the old major releases, but much closer to the former (BTW, there was a "forced" upgrade to the old update releases, too; they weren't supported after a new one was released).
Overall, the rate of expected breakage, if any, should be the same as it was before, but happen more gradually.
(I work on OpenJDK at Oracle, but speak only for myself)
Once you're past 9, it's smooth(ish) sailing. The new feature releases are somewhere between the old update releases and the old major releases, but much closer to the former (BTW, there was a "forced" upgrade to the old update releases, too; they weren't supported after a new one was released).
Overall, the rate of expected breakage, if any, should be the same as it was before, but happen more gradually.
(I work on OpenJDK at Oracle, but speak only for myself)