There's already a working version. Everything has been really simplified and we are trying to take advantage of the new Drupal 7 API so this won't be a plain upgrade. I will be posting here notes about the more important changes so this will be an upgrade log. The main changes so far:
* Events are now actions produced by Triggers (Like in Triggers and Actions). This reduces the complex logic in node and other hooks, and adds a great deal of configurability.
* Templates are hardcoded as classes that produce content for drupal_render(), as opposed to using a different template for each sending method. Then the sending method backend can format the array of data as it fits better for an email, SMS, etc.....
* Complex Queueing and Digesting has been taken out to two new modules (to be upgraded). Just very basic queueing (Drupal_Queue, one event at a time) remains.
There's no upgrade path yet from 6.x versions (work in progress at #1961850: Drupal 6 to 7 upgrade path).