Andre reminded me that there is a problem with upgrading the job queues that have any items in them In https://bugzilla.wikimedia.org/46934.
I would like to include a warning in the installation documentation to clear your job queue before the upgrade, but I don't know that much about the job queue in MW or even if this is possible.
Are there any recommendations for what to tell users?
Imagination does not breed insanity. Exactly what does breed insanity is reason. Poets do not go mad; but chess-players do. -- G.K. Chesterson