Not yet (Destiny)
People have tried to link them to the Taken, but Like the 7 Seraphs, I think some of hit has been postponed for D2 (The Mighty Destinys).
SIVA tends to make symmetrical polygons, and those ships have a elongated diamond shape. SIVA "enemies" are just Fallen, so they don't match the enemy silhouette in the concept art either.
Complete thread:
- Did we ever figure out what the triangular ships were -
ObsidianKitteh,
2016-10-21, 19:09
![[*]](themes/default/images/complete_thread.png "Open whole thread")
- Not yet - Durandal, 2016-10-21, 19:20