I saw some theories about that and some suspects that it could be these silhouettes
and yea they suspects it's a division from the BB pirates, and it both makes sense and it doesn't
It makes sense bc he knew BM was going to Wano and she took a considerable amount of forces with her
but chronologically he said that he was setting sail to " not leave it to the navy " way after he learned that BM was heading for Wano ( so why now ? )
also the way he said it it's like the Navy was going for that thing as well and he was going to clash with them
now i don't think Navy would try to take over Yonkos territories now, so that would mean he probably split his forces a part to go after the poneglyph and a part for the thing the Navy is also going after but that also doesn't make sense bc he not only split his forces to clash with the navy and one with the BMP but he also left his territory uncovered
imho it makes little sense for the BBP to be there now but who knows :V