Unlikely. The issue is that the PTR testing cycle is for tuning, not for the creation of new assets (i.e. new artwork, item properties, etc.). If they were to add a 4th ethereal for DH, they would also need to add one for the other classes for balance as well; that’s a lot of extra work.
The best band-aid solution I could think of was to flag the hand-crossbow as a dagger BUT it would then need the restriction that it would need to disable the use of Rain of Vengeance. Otherwise, it would be too strong with a Natalya + Shadow hybrid (N6/S2) build.
However, this idea may not be easily implementable as there would need to be a clean way to (a) flag weapon types as multiple types (i.e. hand-crossbow AND dagger), and (b) disable particular skills while wearing certain items. If either of these tasks are too hard or time-consuming, then the developers will have to skip Shadow Impale altogether.