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.

Tentative Roadmap

Groovy 1.7.x

Releases

• incremental bug fix releases through 2010

Groovy 1.8.x

Feature set

Here are a few topics we're considering for Groovy 1.8 and beyond.

• internal runtime optimization for better performance
• extended command expression (GEP-3) for nicer Domain-Specific Languages capabilities
• extended annotations (closures parameters)
• more functional aspects to closures (currying, trampoline, memoization)
• support for joint compilation of AST transformations
• modularity of Groovy (splitting Groovy in smaller JARs on a per feature basis)
• native JSON builder / parser

Releases

• Groovy 1.8-beta-1: July 2010
• Groovy 1.8-beta-2: September 2010
• Groovy 1.8-beta-3: December 2010
• Groovy 1.8-RC-1: Early-January 2011
• Groovy 1.8-RC-2: End-January 2011
• Groovy 1.8 GA: February 2011

Groovy 1.9

Feature set

Release mainly geared towards the alignments with the upcoming but delayed JDK 7.

• work related to JDK 7
  • notes on JDK 7 and JDK 8 future
  • usage of invokedynamic and annonymous classloader (JDK7 features)
  • updates for JDK 7 language features (aka Project Coin)

Releases

• Groovy 1.9-beta-1: April
• Groovy 1.9-beta-2: June
• Groovy 1.9-beta-3: September
• Groovy 1.9-RC-1: Early October
• Groovy 1.9-RC-2: End of October
• Groovy 1.9 GA: November

Groovy 2.0

Feature set

• New Meta-Object Protocol
• Incremental compiler
• Improved runtime performance
• Retrofitting Groovy closures to accomodate JDK 8 upcoming closures for interoperability

Other topics we could consider for Groovy 1.8, 1.9, 2.0 and beyond

• ability to pass expression trees / AST nodes as parameters (see C# 4's own expression tree)
• lexical categories
• a symbol concept, a bit like Ruby's :symbol, or like Java interned strings
• co-routines and/or generators
• tail-call recursion
• pattern matching
• parser combinators
• a native template engine compiling to AST (faster, correct line numbers for error reporting, optimized outputting, etc.)
• ...