I think the assertion is that it is not obvious why it would be superceded by Ceylon. So, if there's no obvious reason to move to Ceylon, who is going to get the ecosystem to a level that it will compete with Scala's?
Now, I personally wouldn't be so bold as to suggest that it will always be 10 years behind Scala. I have no idea. But it isn't clear why the language itself is offering sufficient advantage.
More likely, at least to me, is that some of the ideas that Ceylon's shown are practical e.g. union and intersection types, will find their way into more languages because of it.
Of course, someone could produce the next big thing in it tomorrow and do for Ceylon what Rails did for Ruby. Then I'd go find a hat to eat.
The question is: why would you use Ceylon over the competition?
There are a number of reason I can think of. You want to target node.js too; you're a Haskeller in your spare time. That sort of thing.
But the question still stands. Is there enough to prefer it to Scala, Kotlin or, gasp, Java?
Honestly, I don't know. But equally there's nothing that stands out for me. If anything this has actually made me think I should probably look at Kotlin again.
> but I just can't see people choosing the more polished language over the one with ten years worth of library and tool support when there's no USP beyond that polish
It seems all a matter of time. What would Ceylon look like to you after some years of library and tool support?