Few people are expecting Kaguya's spirit to take over someone. Truthfully, it could series. There is only few sensible possibilities Kishi could choose from.
Madara - He has the highest chance, but the not best choice. Madara's death rate is already low with the Juubi inside of him. Naruto gotta save the Tailed Beast. You remove them and Madara won't be able to move. Then Hashirama word's to Sasuke. Hashirama want Madara to live. You add Kaguya, this dude definitely isn't dying. Madara should go out like villain. No last second change in heart. When Infinite Tsukuyomi is stopped, he should go on a killing spree.
Sasuke - Say if Madara does get defeated, and Kaguya's spirit refuse to be defeated. Sasuke is the only cat with the eyes to reactive the Infinite Tsukuyomi if Madara falls. Thus, the Naruto and Sasuke won't bring any new emotion. It'll pretty much be like the Valley of End again.
Hinata - Her being a female Hyuga, and Kaguya being a female Hyuga(Assumed). Making her one of the strongest when she's one of the weakest is a bit too much, imo. Though it would make for very emotional moment. Makes you wonder if Naruto would have the balls to hit her? Until Lord Sasuke come through, slicing heads.
Edo Tensei - They're already dead, so it doesn't matter. Nor does it make it special.
Random Pick - If Naruto get taken over by Kaguya, it would a good plot twist. Then Sakura is the only relevance. Still bring an emotional moment to Naruto and possibly Sasuke.
I'm not sure if Kaguya taking over someone is a good or bad idea for the series.
Madara - He has the highest chance, but the not best choice. Madara's death rate is already low with the Juubi inside of him. Naruto gotta save the Tailed Beast. You remove them and Madara won't be able to move. Then Hashirama word's to Sasuke. Hashirama want Madara to live. You add Kaguya, this dude definitely isn't dying. Madara should go out like villain. No last second change in heart. When Infinite Tsukuyomi is stopped, he should go on a killing spree.
Sasuke - Say if Madara does get defeated, and Kaguya's spirit refuse to be defeated. Sasuke is the only cat with the eyes to reactive the Infinite Tsukuyomi if Madara falls. Thus, the Naruto and Sasuke won't bring any new emotion. It'll pretty much be like the Valley of End again.
Hinata - Her being a female Hyuga, and Kaguya being a female Hyuga(Assumed). Making her one of the strongest when she's one of the weakest is a bit too much, imo. Though it would make for very emotional moment. Makes you wonder if Naruto would have the balls to hit her? Until Lord Sasuke come through, slicing heads.
Edo Tensei - They're already dead, so it doesn't matter. Nor does it make it special.
Random Pick - If Naruto get taken over by Kaguya, it would a good plot twist. Then Sakura is the only relevance. Still bring an emotional moment to Naruto and possibly Sasuke.
I'm not sure if Kaguya taking over someone is a good or bad idea for the series.