I really hope that Kaladin doesn't get another book. He's awesome, but the one book is enough. I want as many people's backstories as possible!
Just tossing these out there: Shen or the Parshendi Shardbearer. I'd love to get a Parsh perspective, I think it would be fascinating.
I also think it's more than likely that one book will go to a character from one of the interludes besides Szeth. I really want to see more of Axies.
My guess is that Kaladin will be the focus of book 10. I kind of assume he'll be the champion that the Almighty mentions to Dalinar at the end of the book. Although, Brandon does have a way of killing my assumptions (**Spoiler Redacted**)
I'd also like to see some more of the interlude characters. I mean, Axies is pretty cool, and that lady who defaces all the artwork sounded interesting. Are they interesting enough to focus an entire book around? Hopefully.
As for the Parshendi shardbearer being a focus character... I only see Brandon doing that if the Parshendi end up being good guys. I mean, the Forsaken are all pretty cool in WoT, and their PoV chapters rock. A book focused around one of them wouldn't work though. So unless the Parshendi end up allying with the Alethi (and how that would ever happen, I have no idea), I see only PoV chapters for the Parshendi shardbearer and not a book focused on him.