Hi!
I don't see WDQ as an alternative. Maybe I wasn't clear enough, I'm talking about the *functionality* of WikidataQuery. So for example WDQ has the feature that I can get a list of items for which certain claims are true. That's a feature.
Matching the features of WDQ is part of what we're looking for in the new service. We do not know yet what the public API would look like, but on discussion page for https://www.mediawiki.org/wiki/Wikibase/Indexing we have some things that the internal engine can do and how they match what WDQ does. So far we're pretty confident we can do the same things WDQ does, but we don't know yet how exactly it would look like :)
Thanks, Stas