This release now uses the Context and ContextDefinition classes from Drupal core to implement parameter variables for Rules actions and conditions. It also includes a ProvidedContextPluginInterface to implement provided variables that are produced by an action or a condition.
You can find more information about further plans and achieved goals in the roadmap.
First unstable pre-alpha release of Rules for Drupal 8. This is not usable at all at the moment and is only intended as developer preview. The code mostly consists of bare bones classes with quite a few unit tests, but there is not much functionality implemented yet.
Note: Rules 2.1 ships with a new translation module based upon i18n. You'll need the latest entity api dev versions and i18n dev versions as of Mar 16th, 2012 or a future i18n 1.5 and entity api 1.0 version.