I think it will be just one version of TI built on Laravel, a major release, however, support for versions 2.x will only continue for 6 months or so receiving minor updates and security fixes while people migrate to 3.x
An upgrade guide will be available to help make necessary changes as there will be loads of changes (mostly in theme) but I'm working hard to make these changes easy or straightforward.
The app's front-end theme definitely needs some touches or better still a redesign, let me know if this is something you can help with.