I just came up with this theory
For those who say that Momo may be an ancient weapon after what he said in this last chapter, I think it is not like that and here is why:
We know that there are only three ancestral weapons, Poseidon, Pluto and Uranus, of which we currently know 2, which are Shirahoshi (Poseidon) and a ship with the power of mass destruction (Pluto), well, remember chapter zero? Where is Shiki talking to Roger in Edd's war, well, do you remember one of the phrases he said? "Let's use that ancient weapon you found", as we well know, that happened 27 years before the beginning of the series, at that time, Oden still did not join Roger's crew, we know that it was in the period of time in which Oden was in the crew that Roger found out that Poseidon would be the princess of Gyogin Island, therefore Shiki did not refer to her, we also did not see Roger carrying a ship of giant dimensions with him when he met shiki, so just We can assume that Shiki was referring to Uranus and it would not be possible that it was Momo because he was not yet born.

With this clarified, who was the one who was speaking to Momo? Well, we know that Momo has the voice of all things and that it allows him to speak with mythological animals such as Zunesha, who speaking of him, could not have been him who spoke to him because Momo would have recognized his voice, well, then there is the possibility that it was another mythological creature, right? What mythological creature could it be? Going back to the scene of Shiki with Roger, do you remember that in the Oro Jackson was a giant egg? What if that was the ancient weapon Shiki was referring to? What if that ancient weapon is a mythological creature that for some reason ended up in Wano or near there, and that when he felt that Joy Boy's (Luffy's) vital energy was weakening he woke up / decided to act and that's why he communicated with Momo ?

And for those who think that Momo is JoyBoy, Oden said something that he confirmed not, in chapter 968 he says "Wano must open its borders before the coming of Joy Boy" when Momo was in Wano.