A development roadmap is produced to forecast upgrades over a 4 -5 year period and is developed as a result of extensive consultation with our community you can find it here. We have four major releases per year (though we are working towards a model of continuous release) and a comprehensive set of release notes are developed throughout each sprint (6 sprints per release) and are permanently available through the community site here.
Releases are available throughout development on the QA server which is available to all customers - and for 4 weeks prior to live release. For access to this test server please contact your Global Administrator who will be able to create you an account.