Did all the other answers to the same question that come up when you search the site, not help?
Nobody who knows the answer can say, so you'll have to be patient - it'll happen when it happens. Maybe with the next release.
Whenever that might be.
The Nikon D3200 may never get tether support as none of the previous models in that series D3000 D3100 have yet to get the support.
It may take multiple releases of LR.x after the initial release of the D750 before the tether support is included.
(for example: Nikon D4s took 8 months 5.4 raw support, 5.7 for tether support)
The 3000 series is not supported by the Nikon SDK. The D750 support came with the November 2014 Nikon SDK. As others have said, it could take a while.