A major project like Cassandra will find that it is easier to use the current version (before LTS existed, people had to upgrade to the six monthly feature releases, but because they didn't get a new version number people didn't care as much). If it does cause trouble, let us know, because LTS really isn't intended for actively maintained projects that want new features and isn't the recommended path for them. Just note that the free upgrade services called LTS are not quite the same; they just include backports from mainline and don't support the whole JDK.
Anyway, I'm sorry about my tone. I know that the change in the version numbering scheme confused people to pick the wrong upgrade path for themselves, and it's our fault for miscommunicating. But I don't know when features will land, or when those who want new features with an LTS service will be able to use them. But I can say that our process assumes that those who want long-term support are trying to avoid new features and are happier when a big feature misses the next release with LTS, so while missing one release normally means a mere 6 month delay, those who wait for LTS for actively developed codebases (even though it's due to a misunderstanding) might have to wait a further couple of years.