I have to agree, if we get SCVI and it is a complete game, this stop-gap installment would have been worth it. But if the series ends here, without a shot at redemption, is just wrong.
I'm sure by this point the call has already been made to continue the series or not. I'm betting they will continue simply because at 1M sales, they had to turn a profit. Especially considering they surely didn't spend any substantial amount of money making this one. The latest Naruto sold less, and you can bet your ass it's getting another installment.
At this point, I am going to say the next Soul installment should be designed for the PS4/orbis/720/Durango/Infinity. This console generation is the walking dead and can not "wow" us any further. Plus to greatly expand the online presence, I think they may end up needing more memory anyway. The lobbies in SCV were a great addition, but they really needed to hold at least three times as many players.