I don't see why they couldnt be ported in. Or if not, why they couldnt just be considered obsolete Dragonriding content, like what the Dragon Isles races will be in the next expansion.
Not to mention, Timewalking is likely to get big updates, and in that scenario a Timewalking zone would absolutely be on the table. No reason why it couldnt just be considered part of that content, similar to how old dungeons are effectively considered Timewalking dungeons currently.