There is no information Grails End of Life or even End of Support for the matter. While Grails 2 (and 1) were developed with the support of Pivotal, Grails is being further developed in Branch 3.
Considering that the switch from Grails 2 to Grails 3 is not trivial, we were wondering if one should take the burden of the upgrade, or leave projects in 2.x branch for some more years.
It all depends on the commitment and the plans of the Grails team. Reading through the documents of Grails, you cannot find any foreseen EOL information for any of the projects.
In Tweeter thought, there was this conversation with the Grails Framework.
The answer of Grails team indicates that Grails 2.x will continue to be support for critical issues (such as security flaws). There is no ETA or deadline for the End of Life Support and that is a pitty.
— Grails Framework (@grailsframework) January 31, 2017
After reviewing the tweet, we decided that projects that we have on 2.5.x branch will not be upgraded in the near future. Seems Grails Team will support on the long run security concerns. Grails 3 offers some nice features, therefore if a project is relatively with not so many plugins, an upgrade might be worth the trouble.