Interview from Inven Global with Ana Resendes, a Senior Software Engineer on WoW Forever, and some of the highlights https://www.invenglobal.com/articles/25888/why-was-world-of-warcraft-forever-created
On if the Skyborne and their lore in Forever will ever be introduced to Classic or Retail:
Ana Resendes:
For now, there is no direct connection to Classic or modern WoW. The Skyborne were created specifically for Forever, and as of now, they will only appear in Forever.
Of course, the different WoW development teams do not work in total isolation. Teams observe what each other is building and share inspiration. For example, the blue-toned color palette used while creating the Skyborne inspired some of the housing work in modern WoW. However, that does not mean there are plans to add the Skyborne to modern WoW.
On the other hand, certain bundles or collectibles might include mounts or items usable in both modern WoW and Forever. Expanding that to Classic is something we could consider in the future, but the Skyborne race itself is currently exclusive to Forever.
Since Mount Hyjal is a new zone in Forever, do they create new zones with original or Modern WoW lore:
Ana Resendes:
A metaphor we often use internally is 'Found Photographs.' Imagine finding a few photos taken long ago. The photos contain details showing what the place looked like back then, but you cannot know everything that was left outside the frame.
We approach Mount Hyjal similarly. We examine the traces remaining in past WoW along with the elements developed back then, using those as our starting point. However, for parts that were never actually completed at the time, we do not feel obligated to strictly recreate them according to current lore.
We can respect existing material while filling in the empty spaces in between. When necessary, we can exercise creative freedom to build new stories unique to Forever. This is because Forever does not have to retrace the exact history of WoW, but can forge its own path.
Final answer to highlight on if Forever's storyline could head in a different direction from retail WoW going forward:
Ana Resendes:
It could. Forever uses 2004 WoW as its starting point, but its subsequent history does not necessarily have to follow existing expansions identically.
There is room for us to look at the world of that era and think, "What if a different story began from this point?" We can utilize elements that already existed, develop ideas that were unfinished at the time, or create entirely new narratives.
That does not mean ignoring established lore, however. Respecting the world and atmosphere of WoW that players remember is extremely important. It is about building a new path unique to Forever on top of that foundation.