We already know his next power to turn into sunny megazord
Or maybe not since him turning into a ship is his bad future lol.
Yeah I think he's gonna have a temporary giant form with merging with the sunny or some kind of raid suit type technology that can be carried in a can and deployed at full size later when needed. (Think capsule Corp tech or pokeballs ofc).
He won't turn into a ship but just a gigantic, stronger version of general franky that the other SHs may able to hop in and control too like a mega Zoro. LMAO AUTOCORRECT I MEAN MEGAZORD!
General franky that will have more features and versatility like the sunny does and doesn't actually skip leg day lmao.
Oda really loves all this gundam/mecha, sci-fi, super sentai(hentai for franky) etc stuff so I'm expecting literally huge things for him.
Elbaf has been too important for him already and Oda has been hinting since he built the Sunny that it will be too.
Imo the SHs will get a much bigger upgrade for the sunny somehow, that will make it a true yonko ship and thus can fit loki on it too.