lol yes, Square Enix has nothing to do with FE.
The Black Knight may be still alive. His body was never found, and he does possess the armor of the goddess (or something along those lines). Furthermore, on the TITLE page shown in FE10:Goddess of Dawn, Ragnel(Ike's sword) and the sister sword Alundite (Black Knight's sword) He may be dead, but he was a too prominent figure, and seeing that his identity is still barely known, I'd say he'd make a return as a prominent enemy in FE10.
Of course, BK only has a chance if Ike is in. So if you think the Black Kinght will be in, you are saying that Ike can be in.
I couldn't see Soren, speaking honestly. I did like his character.
I really want Lyn, and Hecter but their chances are pret-ty **** low.
If Roy is cut, and Marth remains(which seems like what will happen) I'll bet at LEAST ONE fe character will fill the spot. So, I'd guess
Ike
Celice
Leif
BK(if Ike)
and
Lyn, Hecter, Ephraim
in that order. My CHOICE would be Marth, Ike, BK, Lyn, Hecter.