Exactly there are only two choices one is robi and the next is iyer. Rohit is more experienced than iyer but iyer did quite well in this IPL season. Knowing BCCI they will go for Rohit if required but if virat can perform as a captain in the upcoming T20 worldcup then I think they will stick with him.
I would rather prefer Shreyas Iyer over Rohit Sharma. Shreyas is 26 years old and he represents the future of the Indian cricket team. His captaincy was good during the initial phase of the IPL 2020, but later on he made some stupid decisions and received a lot of flak. On the other hand, Rohit Sharma is already 33 years old and he has only 3-4 years left in the international scene.
First Iyer has to cement his spot in the Indian squad, he's still not regular player in the limited overs cricket. I feel that Rohit should get the chance in the short format, even if its for 2-3 years. He has a temperament to guide players likes Shreyas, Gill or overall team, one of them might end up leading India in the near future.