[This is not an urgent request for pre-July.]
Per https://www.mediawiki.org/wiki/Parsoid/MediaWiki_DOM_spec#Language_links the current behaviour is:
[[en:Foo]]
->
<link rel="mw:WikiLink/Language" href="http://en.wikipedia.org/wiki/Foo">
Though this is enough to render, we can't determine what the target wiki language is or the title (in this example case, 'en' and 'Foo').
Version: unspecified
Severity: enhancement