I'd actually be a bit worried if this ended in a Miku confession. Considering one of the points of this arc is to get her to realise that being passive is going to hurt her chances, I doubt any confession from Miku would be an open-ended one like Nino's. Which means either a positive or negative response from Fuutarou. Normally this would be a good thing. However, considering the main plot device of this manga is "Who's the wife?" and the battle between the sisters, I don't believe either result would be good for Miku.
If it was a positive response, then that would indicate that Miku isn't the wife at the end. Otherwise, we'd have the answer to the mystery with possibly two or three volumes left to go (based on the assumption that every girl is gonna get a wedding dress cover). Obviously, if it's a negative response, that would suck for all us Miku faithful, though it could possibly work out if there's more development afterwards. So unless I'm wrong and the end is nigh, I'm worried Miku's story won't end on a high.
I'm sort of coming around to Nino. I had a hard time shaking that dislike of her from how she was early in the story, but I've got a soft spot for people who really care about their family. Watching her being a good sister, in her own way, is winning me over. She could end up as second-best-girl. I'm not sure what Itsuki's angle is here. If events of the past are all she has to bring to the table, I don't see Fuutarou really being interested. He seems to have left those feelings behind.
Yotsuba is great, and I hope we keep one sister who just isn't in competition and is platonic with him. A big part of her charm is that she seems to be above all this, and is struggling with different issues, like trying to support all of her sisters at the same time. Having something else to work with is good for a romance story I think. I was never into Ichika, and I don't think anything could change my mind at this point. Besides her stabbing best-girl in the back repeatedly, she's not even very good at it. We know Fuutarou suspected that it wasn't actually Miku, and now he's had it confirmed. He's gonna pick up straight away that it's not the real one. She's probably gonna get taken down a few pegs in the next couple of chapters. Hopefully she'll go back to how she was before.