The 2.2 modules is planned to be made available via composer as a part of RC2 onwards. (In one sense, that is almost the definition of RC2.) The RC1.* releases have only been on GitHub. If you want to start planning now, you can look at the GitHub repo and docs - otherwise wait until August 14th for RC2 composer repo access. (Being in software for a while, I would add an unofficial comment of don't be shocked if something goes wrong and this slips a little, but things are looking on track…