That's entirely different question, and doesn't really have much in common with iocage/iocell. I, for example, have every single thing I host automated in a way where it doesn't matter wether it runs in jail provided by iocage, jail manually built, vm in AWS or a physical machine. This way, my migration path would be: wipe existing jails, create new ones with new tool, launch automation, done. You, however, might need entirely different approach, based on how your environment/setup looks like right now. One very primitive way would be to simply archive (rsync, tar, whatever else) jail contents and deploy it in jails created with new tool.