We know we need to improve support for rolling courses in Moodle in general. The API supports models that would work with rolling enrollment, but we don't have a model yet.
In your courses, do you have enrollment start and end dates of fixed length? Or do students have a relatively unlimited time in which to complete a course? If you have enrollment start and end dates, I think a model could be built fairly easily that works on a slight variation of the current Target. If you have flexible completion times, things get a bit trickier. You'll need a new Timesplitting Method that will run on a fixed schedule (e.g. every week) and will make predictions about "likelihood to complete" that include how long it has been since the student started working on the course. Again, the API has the elements to support this, but the model has not yet been written.
We are rolling out training in writing models, for those who have some PHP skill, and I'm actively trying to get more development in Moodle to help with model creation without requiring PHP, but resources are tight. If anyone out there is able to help develop such models, I'd be happy to work with you.