Well, as the proud owner of a new HD+ 8x32, I can now report that the HD+ line does have the new field correction first seen (and I suspect, market tested) in the recent Trinovid BR 42. To me this change is at least as significant an improvement as the fancier glass and coatings that Leica advertises for the HD+ line, and yet it goes entirely unmentioned! It may play an important role in how impressed many people are with the view through the HD+, even if they don't recognize what it involves.
I think silence on this subject is a real mistake, given the growing awareness and interest around "flat(ter) field" binoculars today -- I would never have bothered to look at the HD+ model myself had I not suspected that more was going on than tweaking glass or coatings again. Of course it's not a simple question of flat vs pincushion, but a continuum. Leica has found an intermediate formula that delivers a lovely result for me, and probably for most users. But perhaps they think that's just too complicated to talk about?
Clearly not everyone will notice this difference in correction directly. I asked a salesman at Eagle Optics to compare the HD vs HD+ panning across a doorway, and he asked another, and the report was "we don't see any difference, both have some pincushioning". Which they do; the change isn't nearly as obvious, or uncomfortable for some users, as a truly flat field would be.
I think the HD+ line is a real step forward for Leica. And the Trinovid is also a great buy on sale while it lasts. Upon examining reflections in the objective end of the glass, the assorted colors in the Trinovid resemble those of the HD+ much more than the previous HD, which were entirely blue-green. This suggests that the Trinovid's coatings are also more similar to those of the new HD+. (Exception: the coating color on the HD+ oculars is quite different.) One can understand why Leica wouldn't want these models competing with one another going forward.