Oh my gosh I've seen so many speculations for that and I honestly don't know for sure. At first, I assumed it was probably Eren holding Historia's baby considering she's pregnant right now (still mad about that...). To me, that doesn't confirm those popular theories about Eren being the father though (theories of which I've heard enough of). And personally, I'm not a huge advocate for the theory regarding the baby being a reincarnation of OG Ymir. It would make sense if Historia named her baby after 104th Ymir, but that doesn't necessarily mean she's a reincarnation of any sort. So with that being said, I'm not sure who else the child could be. I've been considering what other people have been saying about it possibly being Grisha and baby Eren in the afterlife. I have a strong feeling that Eren will die in the end so that honestly wouldn't surprise me too much. Also, the man's physique resembles current Eren's, so if I had to have a go at it I'd say the man is Eren and the child is a mystery. Not to mention Eren is the protagonist, so I feel like it's only fair that he gets to be on the last page. Either way, the final panel looks promising of at least some light at the end of the tunnel, which is all I can hope for at this point in the story. Thanks for giving me the opportunity to share my thoughts! Sadly I don't get asks very often, so yours is appreciated. :)