Considering our limited human resources and time constraints, it is hard to give definitive and accurate estimates of the milestones we are going to release.
Groovy 1.8 is the current stable branch of Groovy. Ongoing maintenance with minor incremental improvements will be delivered throughout 2012.
You can leanr more about the feature set by reading the Groovy 1.8 release notes.
Groovy 2.0 was formerly known as Groovy 1.9, but considering the important new features, a 2.0 moniker was better representing the importance of that release.
Release mainly geared towards the alignments with the upcoming but delayed JDK 7.