According to Viz's press release, WSJA "will also be part of the upcoming update to the VIZ Manga apps" for iOS but no dates are given. Later in the same press release it states "Each issue may be read on VIZManga.com, and once available, on the updated VIZ Manga App" so I'm assuming even Viz doesn't know at this point when all the details will be hammered out.
I spent 99 cents to try out the first temporary issue and so far it's only viewable in the VIZ Manga web viewer -- it does not show up afterwards in the "My Manga" section of the Viz app.
It's also interesting to note how far WSJA skips ahead:
|Series||Chapter from latest digital volume||Chapter from WSJA #0||Chapter from WSJA #1|
I had thought that the whole point behind Viz's announced "Digital Manga Warp" was to synch up each series by the time WSJA launched but, as can be seen above, that's far from happening yet. Nura is a daunting 138 chapters behind in serialization.
Even if fans were interested in trying out WSJA, it's hard to see how they're supposed to do so as each series has a gap of untranslated material blocking the transition from digital volume to the latest chapter in WSJA. In fact, at this point about the only way for frustrated fans to catch up with the current storylines in WSJA would be to read the material on scanlation sites, which is probably the exact opposite of what Viz hoped to encourage with this whole initiative.