How do I see it? Well if things continue on the path they are now we'll have Nightmare and Seigfried with their own movesets, (Nightmare will have an i7 unblockable that does 180 damage, and none of Seigfried's moves will actually hit).
We'll also have Sophie back, Cassandra, Pyrrha, Patroklos, Rothion (raised from the dead... because Soul Edge... or something), Sophie's uncle and third cousin, and Soph and Cass's brother Lucius, as well as alpha, beta, omega, epsilon naught and chi-squared versions of each one. All of them will use sword and shield with subtle variations between them, except the Chi-squared version for some unexplained reason will have Grieve Edge's moveset. (The reason will actually be explained in the art book, but it will only be published in Swahili and distributed to Ellesmere Island).
About half the rest of the SC5 cast will be in, but they'll be mimics, because... astral chaos... or something. The rest of the characters will be gone, with the reasons only explained in the Swahili art book.
That's how I see the roster shaping up for SC6.