So it says in the over 1 year old rant on Grails 3.0 http://grails.io/post/48599814766/more-on-where-next-for-gra... but it's very slow coming. Same with other Groovy ecosystem software like Groovy which hasn't made a dent in it's new MOP, Antlr grammar, or Java 8 lambda retrofit. And Gradle which still ships with Groovy 1.x.
And while Grails today is a great servlet framework, Grails 3.0 will allow new application profiles, like netty, hadoop and batch.