Currently short extension is used in various places (Vector skin and VisualEditor) and it will be nice for 3rd party wikis to have this feature without installing Wikibase.

Note:

1. Changing the name of existing page property may be considered a breaking change.
2. We may also enable this extension on other wikis, though such description will be overrided by Wikidata description if they are connected to a Wikidata item (it will be used for, e.g. , user pages). We may introduce a tracking category for pages with description overrided by Wikidata (this is useful for other wikis which borrowed short description template from enwiki).

See also:
T213505: RfC: OpenGraph descriptions in wiki pages
T216356: Allow access to the page's local description via the title object
T191531: Create Lua module to expose local short descriptions of pages from other wikis to Lua