Guys i'm pretty sure that Tenguyama Hitetsu is Kozuki Sukiyaki, for multiple reasons:
01. Tenguyama is Old & seems to be same Age Sukiyaki would be now if Alive
02. Tenguyama didn't appear in Oden's Flashback even though he is kinda important indicating he could have appeared as someone else
03. Both Tenguyama & Sukiyaki are both introduced as Kokeshi Dolls Collectors which is Major Hint
04. Tenguyama is wearing a Mask & his Face Shape is exactly same as Kozuki Sukiyaki, also same Height
05. Oden's Swords were entrusted to him even though, again, he wasn't shown in Oden's Flashback
06. Sukiyaki's Death was never shown, Oden never confirmed his Death
07. After saving Wano, it's possible that someone else will temporarily rule Wano with Momo & Sukiyaki is perfect pick
08. Tenguyama said he is waiting for someone for a long time & yet again, he wasn't shown in Oden's Flashback
09. Biggest Hint is so far is that Toei announced that the Voice Actor of Sukiyaki in Oden's Flashback will be same as Tenguyama !!!
10. As someone who can read the Poneglyphs & is Old, he might have Important Role in Post-Kaido part of Wano Arc
... etc