Datamining confirms nothing, they also datamined Warforged, which doesn't make much sense apparently
that said, i'm pretty sure we'll be gztting duergar, dont worry
Not an argument.
Datamining helped people to come up with a mod that let you play as a duergar, including voice lines of NPC addressing you as one already.
The same isn't true for Warforged, which are barely mentioned.