Earlier quoted context omitted.
Can you explain why you think so?
Most of the selling points on scala-lang.org still apply over C# - type inference, pattern matching, case classes (C# makes these less bad than Java, but the field/property distinction can still bite you), an inheritance model that supports the good parts of multiple inheritance without the problems, covariance/contravariance, for/yield syntax that's generic and user-controlled, higher-kinded types. It takes a while…
That's not true. You can extend the language yourself with "computation expressions" (and that's in fact how the 'async', 'let!' et al keywords are implemented).