List view
v3 would be when MODX itself is composer compliant and Repoman would be used to manage MODX itself, a site's modx-packages (i.e. MODX Extras) and any dependencies they have.
No due dateVersion 2 is when Repoman functions as a Composer-Plugin and can be used to resolve dependencies. At that point, it would act as a full replacement for the MODX package manager (MODX itself may or may not be composer ready at that point), but a single MODX site would have a single composer.json file to manage its components (i.e. extras) as modx-packages
No due date