I get it now Shirahoshi is Mosa, but what does she has anything to do with Elbaph arc? She is on the opposite end of where Elbaph is located. Is she going to swim through the sea serpent current to reach Elbaph and save Elbaph with the aid of Sea Kings? I know the sea kings can pull Noah Ark and it's very huge, but it is the purpose for fitting the giants on it? I really hope not so.
Could be more evidence of Loki either
A. Truly joining the Strawhats
Or B. Temporarily joining to save Shirahoshi who’s likely being kidnapped by Blackbeard (should be easy, most Fishmen including Neptune are fodder)
With Caribou revealing the locations of both Pluton and Poseidon I wouldn’t be surprised if we ended this arc finding out that he already possesses both
Remember, time passes differently in Elbaf (1/3 conversion iirc) so by the time we leave a lot will have changed on the outside