Is the information about the Elves confirmed? Or is it still just speculation?

Then they will probably remove the Druids... Although, perhaps a nature mage could be a hero... Although the word "Druid" is clearly more accurate. They might also remove the Dancers. I'm probably still in favor of keeping the Druids in the faction. The Dancers don't suit them as well. But as long as it's not a Ghoul4 :(:D.

There was a hint: "...if I say that the 4th faction was present in all parts of the series, you will immediately understand which 4th race I mean...". And about the Elves, these are my assumptions, and there have already been enough hints...
Yes, I also think that the Druids will become heroes, although they could also make some kind of shaman a hero-mage. And the Dancer really doesn't fit the faction, I hope they will replace him, not the Druid. I think the creature that was in earlier games is the Pegasus Riders. I think it will be like this:
core: Dryad, Dancer or Druid, Elf Archer
elite: Pegasus Riders, Unicorn, New unit or Ent
Champ: Novice or Ent