I can't say I foresaw the doppelganger element whatsoever, but I think everyone knew Himawari was responsible for the looping.
We also knew Kaede was also important but it was just very cryptic as to how. I like how they tied it together.
Also, in chapter 8, Kaede and Himawari have a conversation about Hima rejecting Tsubaki. And Kaede points out that since Tsubaki was the one that helped "shape" Ota into who he is perhaps Hima was projecting her feelings that were actually for Tsubaki onto Ota. I think this alongside that Hima chose Tsubaki as the anchor for the looping tells me she liked him all along. Perhaps what happened in 4th grade will confirm that I don't know, but like Tsubaki said finding that out is the key to everything.
Thanks for the translation!