Risker,
You are right that it will undoubtedly get used as soon as it is available, and it is unfortunate that it will presumably get deployed without any agreement having been reached on wiki about how it should be used.
However, when it comes to an area like infoboxes, I think a lot of hardship could be avoided if the community can ultimately come together and adopt a sensible set of guidelines for how wikidata should be used.
For example, one of the reasons Commons is able to work reasonably well within the global context is that every wiki ultimately has the option of ignoring it and uploading locally preferred files instead. I would argue that the use of wikidata in infoboxes should follow much the same principle. Specifically, templates ought to be engineered such that values are obtained from wikidata only when no corresponding value is present locally. So for example, one might have an infobox with a field for birthplace. If enwiki specifies birthplace = Athens, Georgia, then enwiki will be guaranteed to display "Athens, Georgia". And the template should query wikidata only if the field is omitted. So, if birthplace= is left blank, then we might ask wikidata for the answer, and can use the value recorded there, but only so long as no value was filled in locally. That's the kind of behavior that I think makes sense for infoboxes. Decisions about when to rely on local values and when to rely on wikidata are obviously an issue were guidelines are needed. For example, I'd argue that wikidata should never be used to define elements that are likely to be controversial or subject to dispute (e.g. Gdansk/Danzig). It could be a reasonable policy that controversial data values should always be retained using strictly local input. That would limit the potential for controversies over wikidata values from spilling into Wikipedia.
Unfortunately, I suspect we are going to take a while finding our way when it comes to wikidata interactions, though that doesn't necessarily mean we won't ultimately have coherent policies on its use. While obviously a bit late in the game to be starting now, I think many people would welcome a discussion on wiki of what best practices for the use of wikidata ought to look like, and I'm sure your input could be valuable to that discussion.
-Robert Rohde aka Dragons_flight