Release plan is used in software development and software release lifecycles and varies depending upon the software development methodology that is used. For example, in the traditional waterfall model (Requirements => Design => Implementation => Verification => Maintenance), it is expected to release the initial software version prior to the Maintenance phase, then subsequently increase version numbers as bugs are submitted and fixed in the Maintenance phase. However, in SCRUM methodology, for example, Release plan is dictated by tasks/features/bugs
that are organized in 30-day sprint cycles. Due to its flexibility, Redmine can support various software development and project management methodologies.
For a list of current software development methodologies and their pros and cons visit the Wikipedia article https://en.wikipedia.org/wiki/List_of_software_development_philosophies...