Oda's trolling with these silhouettes. But I'll go with Occam's Razor and say it's Hiyori.
The Scabbards are now a liability in their state. Someone has to protect them. To me, this now gives some credence behind Orochi's revival. He may not have control of the operation anymore, but if he can exact his vengeance on the Samurai who've been tormenting him for 20 years, he'll be satisfied. He's that petty. And if Hiyori confronts him, then it ties up the Orochi/Komurasaki thread, as Orochi will learn she and Hiyori are one in the same, she tries to enact vengeance, etc.
When we last saw Yamato's group, Yamato appeared to be readying themselves for battle. Yamato could ask Shinobu and Momo to escape while they hold off the mysterious enemy, and when they (Momo and Shinobu) do, meet up with the beaten Scabbards, Hiyori, and potentially Orochi. Seeing his family in danger, this could be the moment Momo finally steps up. He's been training all arc to prove himself.