The OCI Grails team announced the release of Grails 3.2 Milestone 2, which includes GORM 6 Milestone 2
They describe the GORM release as the biggest release ever!
There are many new things about GORM 6. For example, I talked in a previous issue about RxGORM. The ability to use GORM without Spring is a huge thing and I think it will increase GORM adoption beyond Grails apps and into other frameworks and apps.
Blog post by @WhyPhilip which summarises some of the challenges you will face while migrating from Grails 2 to Grails 3: New Tech, Configuration, IntelliJ, Plugins.
The post is 8 months old. I believe some of the described issues are now solved. Nonetheless, they are good points. Written in June 2016. I will recommend anyone performing a migration to read as many posts as this one as possible. Search the archives of this newsletter, I've linked to a couple of similar posts already. It will save you some valuable time and give you a better understanding about the changes you will face.