Hola,
Due to changes in the donation system, it would be more practical to reshape how RS6 is released. Initially the plan was to do some essential updates to the current game mode and introduce a grand release for RS6. Realistically this won't work with reduced funding, rather we will switch into a periodic release schedule.
Versioning? RS5.1 and greater conforms to a semantic versioning scheme.. at least it did when I was around and it shall now. In complying with that, a patch occurring in April will introduce a change which would qualify as "RS6" as such that'll be the first introduction of RS6.
A roadmap will be made available once it has been reasonably adjusted for this new schedule.