A difference with Java is that new Java releases tend to come with changes to the JVM. The language's semantics and the abstract machine are intertwined in a way where the JVM might be changed to enable a new language feature, or vice-versa. And the JVM itself improving is pretty much always an unalloyed good, so people tend to look forward to releases of Java to see what JVM improvements it has in store.

Elixir doesn't hold the same position for its abstract machine. BEAM, the abstract machine, has its development intertwined with that of Erlang's language development, but not-so-much with Elixir's. Elixir can stabilize while BEAM+Erlang continue to evolve "underneath" it. Given that Erlang syntax is pretty much† always valid Elixir syntax, Elixir doesn't even need to change to expose new Erlang stuff!

† There were big changes when maps were introduced, but another change of that scale seems unlikely at this point. (Unless Erlang gets a mutable byte-array type or something.)