I wouldn’t be so sure that we are saying goodbye to highlander decks. The first card to be revealed is an image showing the belt of Kazakus. As you mentioned in this post, Kazakus was a part of the second batch of highlander cards that came a year after league of explorers.

The timeline kind of matches and I can see the classes that did not get their own highlander card be rewarded with one and the classes that didn’t get galakrond will have a similar type of hero card or hero cards of their own to help give them an edge. Just my guess.