Which community should be consulted on this technical decision? What if enwiki wants prolog and dewiki wants lua and enwikitionary wants javascript? Occasionally technical decisions have to be made by the developers. The templating language is a technical decision. It's really not something that is up for editor community debate.
This decision was hashed out over months (really a couple of years if we consider the original iteration of this idea) with the developer community. If the editor community wishes to take part in these kinds of decisions, they should join wikitech-l.
Most lay users likely won't be able to understand the discussions that take place on wikitech-l. Hell most lay users don't even know it exists.
While I won't weigh in on whether or not the choice of Lua was our decision to make or not, I don't think that the argument that editors should join wikitech-l is a good one.
Perhaps the ambassadors mailing list? But wikitech-l? No.
I am curious though to see if we ever even mentioned this idea to the editors on at least enwiki though. I think such knowledge would greatly help everyone else here in evaluating whether or not we included the community enough on this decision.
Thank you, Derric Atzrott