You need to already own the Warglaives on a character on your account to get the DH version from Timewalking Black Temple. There's no 100% here. If you have the DH version right now on live, you will have the old version on every class that can use them when 8.3 comes out, unless you deleted the Glaives for some weird reason.
DHs had to go through the same process as every other class will have to come 8.3, in addition to getting an Illidan kill in TW BT. Their reward was exclusive claim to transmogging the Glaives. They're losing that exclusivity while the other classes don't have to wait for TBC TW to be active to get their own transmog.
I do wonder if there will be a difference between the two versions of the Glaives. If I remember correctly, the DH version sits differently on the character's back, or was that reverted?