If they know, they are probably contractually obligated not to say.
That said, if Nikon supports it via their SDK (which they did effective 11/12/2014 - too late for 5.7), it likely will be added to Lightroom's tether support. Normally tethered support lags behind a version or two from Raw file support.
Thanks for the info Rikk, looking forward to that. Be nice if they could support customers more efficiently though. With the way technology advances, and being the worlds biggest camera manufacturer, updates should be pronto and scheduled with camera release one would like to think. Oh I know....I'm dreaming, lol.