Thanks to David's comment earlier today about editing , I found this page in the Russian Wikipedia:
https://ru.wikipedia.org/wiki/Module:Universal_infocard

It's a Lua module that shows a person infobox, pulling the data from Wikidata and without giving any parameters in the wiki source code.

This is essentially the fulfillment of Wikidata's promise to make editing articles with infoboxes easier, and it's wonderful. There are more things to do, but I already want to thank everyone involved.

But now the question of cross-wiki synchronization arises. Wikidata.org is cross-wiki by definition. Templates such as {{Universal infocard}} should be cross-wiki as well.

Why? To make translation easier. The article about the Slovak poet Bohuslav Tablic is available in Russian, but not in English. I'd love to translate it to English, but I'll have to use {{Infobox writer}} and fill it manually with data. This is doable, but it would be far more efficient to pull the data from Wikidata. This will become even more acute when the ContentTranslation, and that should happen Some Time Soon. Millions of such articles could be translated, and using Wikidata well will save the translators millions of minutes.

I am not saying that all projects should have the same templates. For example, I am not concerned with the visual design of the templates - this is up to the communities and the designers. But the way in which the data is used should be sync'ed.

What does it entail?

Synchronizing the code of the Lua modules? Can these, maybe, be made into a Lua library that is maintained in MediaWiki source, rather than as on-wiki modules?

Major cross-wiki collaboration in functional specification of data to be used in infoboxes?

What else?