I agree with most of what you say, and obviously, some people really like Scala, and not only as "a better Java". But I think there is still an objective measure here, which is bang for the buck. Scala does let you choose different styles, but while you pay in complexity for that choice (which some people like), you don't get the same benefit as you would in an ensemble of languages. Scala really is heavier than JavaScript, and Scala doesn't really give you most of Haskell's benefits (no true type safety because of casts, no control over side effects, and easy mutability). So you pay full price for "good" ADTs, but get just a taste of their benefits. Same goes for duck typing and macros.
So you do get choice, but it's more of a choice between a Paris-style and a New York-style Las Vegas hotels rather than between Paris and New York. Scala is Las Vegas, only it runs on the JVM which offers cheap supersonic flights between Paris and New York.
Also, the kind of team you describe can't really be a big one. I might see it working for 15 people; maybe 20 if they're really good. But 50 and up? I don't think it's going to work.
So you do get choice, but it's more of a choice between a Paris-style and a New York-style Las Vegas hotels rather than between Paris and New York. Scala is Las Vegas, only it runs on the JVM which offers cheap supersonic flights between Paris and New York.
Also, the kind of team you describe can't really be a big one. I might see it working for 15 people; maybe 20 if they're really good. But 50 and up? I don't think it's going to work.