@MaxSem doesn't think we should SWAT this and, after reflexion, I concur: the guided tour has well been tested on en. and other wikis, but to enable to all wikis is indeed something more like a new feature.
@Mattflaschen-WMF a dedicated deployment window would be better so, when do you think we should plan this?
Actually, I was wrong, or his edit is wrong. It's at https://wikitech.wikimedia.org/wiki/Deployments#deploycal-item-20170425T1100 (11:00 UTC Tuesday/04:00 Pacific). So, yeah, 5am on Monday is still open.