If there is a new book as "Libris Mortis" we should ask about the "deathless", a monster subtype as undead, but healed by positive energy and hurt by necrotic damage. This may be a monster ally.
If there is a return of the demiplane this can't be only a crusade against undeads, or the PCs would get magic item to become "ghostbusters". The players should face other type of menaces as shapeshifters, fomorians with mutations, monster plants, abominations from the Far Realm, constructs or dark feys. The dark feys should give good reasons to cause fear to monster PCs.
If a crossover between the demiplane of dread and other setting (Innistrad, Masque of the Red Death) is possible, the planning should start now to can create a good plot and avoid the risk of a "jump the shark" effect. And I notice there are pieces of a real complex plot. This could be like "Game of Thrones". The authors have had got enough time to rewrite the story.
Today some players want to play monster PCs. Why not if vampire was a monster class in 4th Ed? And the Ghostwalk where the PCs could be ghosts.
And some player will want to play like a shaman, a necromancer who summon deathless spirits as a ghost-type pokemon trainer, or the main characters of Shaman King manganime.
* What happened to (original) Barovia in the prime material plane? What the hell was the king Barov von Zarovich VI? (Strath's father was only count) Could the "crystal sphere" of the planet where Barovia is to become a "spin-off" of Ravenloft?
* What could happen in a second grand conjunction with new time travels?
* What if the demiplane of the dread is a time loop? After an(zombie) apocalypse there is a reboot and start again.
* Have you got your own ideas to be added for your future adventures in Ravenloft? For example soulfuse, sentient constructs with incarnum soulmelds, or ushabti, like a mixture of deathless mummies and living construct to be played as a PC race.