Groovy just released 2.4.6 - I think it's worth bumping to this version for TinkerPop 3.1.x/3.2.x. I was scanning through the bug fixes and there are more than a few items there that I think we should have available to TinkerPop. I'm also aware of some code changes that would allow me to drop some custom code out of TinkerPop that was working around a problem or two from previous versions of groovy.
Here's the changelog for that version: http://groovy-lang.org/changelogs/changelog-2.4.6.html Barring objections in the next three days (Thursday, February 25, 2016 at 6:30am EST), I"ll assume lazy consensus and move forward with the change.