We like the new next-gen template quite a lot. One thing I've found jarring is that the epic due date is in no way connected to the stories' sprint assignment.
I understand a blocking issue is that future, not started sprints cannot have dates now (why?) but it would be great if Jira would either warn me on the roadmap or the backlog view if there is a story to be done in the epic outside the due date, or maybe set the due date of the roadmap item accordingly.