This warning only applies to servers running Hubzilla dev branch!
I have just tagged version 4.7.2 in Hubzillas dev branch. This marks the point after which we will start merging stuff related to the zot6 transition.The dev branch will become very unstable* after this point!
*Since you are already running dev branch i will not mention that it could eat your kittens, empty your fridge or do other nasty things...
If you feel brave, go ahead. Otherwise consider checking out the 4.7.2 tag and stay there until the warning will be suspended.