This feature is for all non-LDS packs. When the school year is over just use this feature to transfer the den leaders and scouts to the next den rank.
This feature will maintain the same den number and your iCal and Den Forum (if enabled) will continue to work so you don't lose historical data.
If a leader was registered as a Tiger Den Leader (TL), after the transition they will become registered as a Den Leader (DL) and their Positions page will reflect the change and keep a record of their tenure.
Same for advancing Bears to Webelos. The new positions (WL and WA) will be reflected on the Positions page.
To advance your den to the next rank go into the Edit Den page.