ALWIL Software is currently redeveloping ADNM and the last info I heard was the product will be split off into a smaller business edition and a larger ADNM edition. Depending on what version you install, the process may be different. Of course, the product isn’t out yet so it’s hard to tell how exactly the process will work.
Upgrading from 4.6 to 4.8 was as simple as running an update task on ADNM. The managed clients were pushed the update (no uninstall was necessary).
I’m sure once ADNM v5 is more complete there will be a lot of discussion on how to upgrade.