It is possible to upgrade the OS without downloading each OS version between the existing one on the datalogger and the most current one available. For example, a CR1000 can be upgraded directly from OS 14 to OS 25. However, when a large jump in OS versions is made, the upgrade will likely restructure the Status table and the Setting table, and they will need to be manually reloaded.
Note that in many instances, an OS update may not be necessary. Before updating, check the OS Revision History to see if a newer version would provide desired benefits.