Would it be dark? Would it be light-hearted? Would it be the last in the series?
All of these are questions without answer.
As far as my knowledge goes:
Curien's Son: Fine, possibly in a relationship with Lisa
Lisa: Fine, p0ssibly in a relationshop with Curien's Son
The Magician: Probaly fine, I mean. He has came back 3 times now, why not 4?
Dr. Curien: Dead, unless he is brought back again like the Magician
Gary Steward: Unknown, possibly dead, may of been the Star in HOTD 4 so he is probaly dead.
Sophie: Unknown, possibly undead or dead or alive
Goldman: Dead, but he could come back
It could be that Dr. Curien (The wheel of fate) The Magician, The World and The Star could be joined together in one to create the deadliest zombie/beast ever in the series?
Could there be a baby in the sequel?
Could it just be a dumb reboot?
Could it be that Sega will go bankrupt before a sequel/prequel/reboot comes out? (Sega does do XXX Sonic stuff. THE kind of stuff.)