Blizzard have said in the past that updates to models are best justified when they release content where those models will be present, so they get a lot of use. That's why we got updated demon models when they released Hellfire Citadel and were preparing the Legion expansion. The reality is that those models were already developed as part of the patch and the next expansion.
So with them giving us a new abomination model, could that mean they had that abomination model already developed as part of the work they put into the development of the next expansion?
It would make a lot of sense, seeing as Legion had us return to a lot of familiar and popular themes: Legion, Demon Hunters, Vrykul, Titans, Old Gods etc. Wrath of the Lich King is together with The Burning Crusade among the most cherished expansions, if not the most cherished expansion of them all. Bolvar was involved in the beginning of Legion and throughout the Death Knight campaign. It would make a lot of sense for us to return to the Undead theme in the next expansion, if only for the fact that players would love to return to Northrend.