For instance, new work on the successful product is needed only once every 2 months or so when users provide feedback. So a team is needed to do that work. BUT, when there is no feedback, then what do you do with the team? Let them sit idle? Give them random stuff to work on? Specifically, what do you get your team to do when you don't have a concrete idea / new product to work on?
Ask the team. What do they think is a good use of their time? No one likes to sit idle. If they were on a heavy schedule to meet the product launch, some downtime is useful to regenerate creativity, energy and focus. Have they documented all the processes used? Have you conducted a post-project review of what worked and what didn't and what could be improved next time?
These are some things for a temporary lull, however, the bigger question is how to engage your team when there isn't work to do. Can the team handle more projects?