Everything depends on 2 factors:
1. What is Jorge Lorenzo going to do?
2. Does Spies want to go to GP's next year?
If the answer to the first question is that Lorenzo will leave, Spies would get the FIAT Yamaha ride, and then Crutchlow would slide into the factory WSBK team to be partnered with Sykes. I think this is a bit of a dream move as I don't think Lorenzo will go to HRC, therefore I think this is out of the question.
The answer to the second question is a little bit more interesting. I think everyone knows that Ben wants to go to GP's next year, but he is not as stupid as others were in going there on uncompetitive machinery. I think he will wait until he can get a competitive ride (meaning FIAT Yamaha, Repsol Honda, or Tech 3 Yamaha.) I didn't include Ducati because Stoner is the only one that has been quick on it consistently, and I'm not sure he would risk it.
Therefore that leaves Rossi, Lorenzo, Dovizioso, Pedrosa, Edwards, and Toseland as the candidates likely to lose a ride.
Obviously Yamaha is keeping Rossi, and most likely Lorenzo so that ride is out.
The Honda would be too fragile for Spies lanky body structure, and Honda it seems wants to keep Dovi and Pedrosa with recent news stories coming out. They are also going after Lorenzo so it seems like Spies is not on their radar.
That leaves just Yamaha Tech 3. I honestly believe this is where Spies will end up going next season. He has shown the consistency of a mature rider that is so quick that he deserves a shot. Who will he replace?
I think it will be James Toseland. Colin Edwards has been a Yamaha man throughout most of his career and about the last 4 seasons in GP's. He has shown his dedication for the brand and has always given his all. Unlike Honda, Yamaha will not betray one of their premier riders. But it's not like he is slow either... He is the best satellite rider currently fifth in the championship in front of Dovizioso, Vermeulen, Capirossi, Elias and Hayden who are all "on factory equipment." I think that statement says how good the Yamaha really is, but as well as how consistent Edwards is.
Plus Rossi really likes Colin, so it would not surprise me Vale adds his two cents to the conversation if they thinking to send Colin back to WSBK. I think CEII has also earned his ride to stay in GP. That would mean Spies would come in for Toseland, which would bode well as Ben and Colin get along well, not to mention he could act as a mentor in his first season. I'm sure Spies has settled well in Italy, but nothing helps more than having a fellow countryman as well as a Texan in this case be on the other side of the garage. He would help him understand the nature of GP's. Spies has had exposure to it, but not a full year of it.
That would leave Sykes, Crutchlow, and Toseland contending for the Yamaha WSBK rides. Honestly I would see Sykes staying as Meragalli has stated he wants Tom to stay. Therefore it would be between Crutchlow and Toseland. Honestly I see Toseland getting the ride due to his experience, but he has stated multiple times that he wishes to stay in GP so it wouldn't surprise me if he got a ride at Suzuki or a satellite Ducati. We all know that would spell an end to his GP dreams, but I think he would want to stay rather than go back to WSBK. That would open up the door to Crutchlow to go to the Yamaha WSBK squad partnering Sykes.
IF James is smart he will go to Yamaha WSBK if he gets rejected by Tech 3. But Yamaha won't want to lose Cal, therefore they might create a third bike in WSBK for him sort of like Kiyonari has at Honda, or risk losing him to a Moto2 ride, which Crutchlow has gone on record saying he wouldn't mind as it would speed up the possibility of going to GP.