So on this issue I currently only speak on the "bulk updating" issue and I would like to note that I do not speak for the discovery team who have the most focus on both geodata and Wikidata. However I do have a decent passing knowledge about this:
This is a pretty complex issue compounded that geographical data has historically been pretty unloved over the years not just by mediawiki (wikidata support as well) because it is an extremely complex thing by it's very nature.. Unfortunately this leads to click bait by people like the National Geographic "Australia Is Drifting So Fast GPS Can't Keep Up".
*1)* *GPS does not equal GDA94 * Firstly GPS itself is not changing at this point (It does get periodic adjustments but this is not one of them). In this instance it is that Australia is moving from one conventional datum (GDA94 https://en.wikipedia.org/wiki/Geocentric_Datum_of_Australia_1994) to a new conventional datum with the aim for it to be used in perpetuity - GDA2020 ( http://www.icsm.gov.au/geodesy/modern.html - No wikipedia article, I should probably write it) and also at the same time creating a new reference system ATRS (Australian Terrestrial Reference System - https://en.wikipedia.org/wiki/International_Terrestrial_Reference_System).
GDA94 uses the exact same number system as WGS84 ( https://en.wikipedia.org/wiki/World_Geodetic_System) which adds to the confusion.
Which leads me to point 2 -
*2)* *Wikimedia Coordinates are assumed to be WGS84 * Wikimedia has typically used WGS84 coordinates because of their universality especially on the web ( https://en.wikipedia.org/wiki/Web_Mercator). Generally we don't support providing local cartographic grids within articles (at least not I can't seems to find such support) Unfortunately what this means is that we have to assume that grid references we currently use and store are WGS84 coordinates. However this comes with problems because sometimes WGS84 is updated as geodetic and dynamic plate models improve. There is additional vital metadata needed for this.
Unfortunately we currently do not store that information within Wikipedia articles or which leads to point 3 -
*3) Without the correct metadata, it's impossible to the job well * Because currently there is no clear indication within Wikipedia articles and as far as I can tell within Wikidata as to both what *datum* and what *version* any particular coordinate relates to, there is no guarantee that any particular coordinate would be any more correct than it was before.
Going forward we should really should greatly increase the amount of support for geographic metadata within Wikidata. As a result coordinate updates, even fairly minor ones, create inordinate amounts of unnecessary work for volunteers. Good metadata with allows us (either WMF or volunteers) to use translation models that should allow us to be able to maintain such data with minimal volunteer overhead. Without it, it's a headache.
I hope I explained that well... Make sense?