Opaque types are not a "small OOP improvement", they finally bring zero-cost newtypes to Scala, superseding value classes. Now you can finally ensure that object Ids, people's names, meters, feet, and degrees Celsius all have different types - without any extra boxing at runtime.
Your list is also missing typeclass derivation, which is going to be a fantastic quality of life improvement. Yes, even for people who don't care about what a typeclass is.
This is a point I want to stress the most, I think. Features like type lambdas, or libraries like Shapeless - they can possibly be extremely beneficial to you even if you don't use them directly in your code. Ask your nearby Haskell programmers about the virtues of `deriving (Eq, Ord)` and they'll talk your ear off. And that's before they even get to things like `deriving (FromJSON, ToJSON)`. Don't have a Haskell programmer nearby? It's ok, ask a Rust programmer about Serde instead. Typeclass derivation is just such a massive, massive feature to have in your language's repertoire.
Edit: oh. And this is on top of a rewritten, faster, compiler, a unified base paradigm making it easier to learn the language, and better error messages for compile errors. I think dismissing this as as minor release is disingenuous to how much effort goes in such a large scale rewrite. Granted, most of it is under the hood but it will pay off dividend.
Support features of JDK 11+ https://github.com/scala/scala-dev/issues/139
Support Java Module System https://github.com/scala/scala-dev/issues/529
In comparison language features seem to attract much more attention:
Removing existential types https://contributors.scala-lang.org/t/proposal-to-remove-exi...
Significant indentation syntax https://github.com/lampepfl/dotty/pull/7083
Eventually they won't keep up with the underlying platform.
Java is a pretty safe bet, as it has an outstanding backward compatibility track record.
* True intersections and union types -- use them sometimes, not something you can't live without though.
* Trait parameters -- slightly easier life for OOP, ok I guess.
* Function types and implicit function types -- right, will make your code even harder to read (subjective).
* Generic tuples -- again, I can't remember we ever had problems with tuples in Scala.
* Opaque types -- another small OOP improvement.
* Type lambdas -- I've never seen them used.
* Erased parameters -- probably useful if it improves performance even at the cost of readability right?
* Enums -- finally something practical, good.
And that's all about major changes in Scala 3. Ah, yes, we get a new compiler. Are you excited?
These changes look like a quarterly release than a major version shift. Now, imagine a project manager who's estimating the migration downtime for Scala 2 for the sake of the above.