This has been discussed several times in this thread. no one knows for sure. Some have theorized that you would not have to go back, but we elk only know for sure when the ota comes out. Also on that topic, an FDR will not put you back to .211. It can be done however, i don't remember how. I'm sure matty can chime in if we need to go back
There is a factory fastboot file available that will get you back on OTA .211 that would put you back on the upgrade path if .214/.215 broke that path.