Scala 2.12 and Kotlin 1.0 release points should roughly coincide. Scala's got a wee bit of a head start, but if Kotlin delivers on the promise to compile as fast as Java, then for sure they'll gain traction.

Speaking of build times, just got back from the ScalaExchange conference in London (suprisingly large turnout, a little over 400 attendees). Talking with one of the Typesafe team members, it appears that Jason Zaugg (works on the compiler) recently found a way to reduce build times by 20-30%...and that's just for 2.11, good times ahead ;-)

Should point out that incremental builds + sub projects pretty much completely mitigate the "scala is slow" argument, but for deployment Jason's recent enhancements will be a boon to all Scala teams, large and small.

    Scala  - about 10 years old
    Kotlin - not yet released