Whats happens to the app after 120 days?

The app would still be visible in the stores and for those who downloaded it, you would still have access to it. What happens to it, as is the case with “expired” single event apps is that the line of communication between the app and the CMS is severed. As a result, no content can be updated nor can things like delegate to delegate messages be sent or the results of any poll/survey be communicated from the app, to the CMS.