I don't wanna get too heavy on power level discussion or anything of the sorts so I'll just make it as simple as I can.
I'll be pretty honest, since the moment I saw Shiggy crumble Re-Destro's Stress Output Burden attack to a literal shockwave that decimated all of Deika city it left me in a strong state of awe with how far he's come as a character. Of course, this whole post isn't going to be me kissing ass or anything but rather asking the question; given his current development in the story and eventual soon to come further increase in power, will Shiggy be or NOT be the final villain of the series.
It genuinely gets me curious because when I see the likes of Overhaul and High End (I brought a Nomu into the mix, go figure) and how insanely powerful they are it makes me wonder if there's possibly a far stronger villain in hiding, one of which surpasses even the likes of All For One. I personally thought it would probably be the luminescent baby from the first chapter, but hey, that's just what I personally thought, not being serious about it.