So every user can commit only to 5 sites on Area51. If a site I committed to reaches private beta/public beta/final release, will I be able to use commitment I spent on that site again? Or I can only commit to 5 sites ever?
Once a site exits beta, you are free to commit to another site. Even before the site goes to beta, you can un-commit to apply your commitment to other sites. The idea is that you only have three outstanding commitment "tokens" at any one time.
So the moment it exits beta, your commitment should be freed up for use on another site.
EDIT: We changed the way this works. Once a proposal enters the beta phase, your commitment "token" is only freed after the site exits beta.