This is a really good question, I would really l like to know how this could work too :-)

@kwatkinsinatl  -  Pretty sure that if you have the waitlist turned off, when users enroll they would then be in an ‘ENROLLED’ status at course level pending enrollment into a session.  If the Waitlist is turned on, their course enrollment status is ‘IN PROGRESS’.  When you have new sessions you could then filter to the ENROLLED users at course level and send them an email to enroll in the new session.  Additionally there is a notification that could be leveraged that notifies when a new ILT session has been created, but this may send to all users in the course vs just the ones who have yet to complete,  That may need some testing to confirm.  Hope this helps!

I believe…

The course waitlist

is when the maximum number of enrollments have occured on the course level (total) enrollments. This settings is found under Advanced Settings > Catalog Options > Maximum Enrollment Quota

The session waitlist

is when the maximum number of enrollments have occured for the session. This setting is under session properties Maximum Enrollments. 

If users are being placed under the course waiting list, I would assume that the course maximum has been met. 

(Sorry my original answer was not very helpful to the original question, I misunderstood the question) 

What we have been doing is after the first event the instructor/producer is using the send email feature to send an email to the waitlist users letting them know they are being unenrolled from the session since they didn’t get into the course. Then they unenroll them from the session giving them the ability to enroll into a future session.