I've said it before, but I see no reason why Chrom getting in would mean Ike has to get cut. I want both, my want of Chrom is not indifference to Ike. Ike is actually my favorite lord so I'd be pretty sad to see him go. I think the only reason people think Chrom may "replace" Ike is because they view Ike as having replaced Roy. In some ways that is true but it's not completely the case. While it's not common knowledge to most gamers I'm sure most frequenters of smashboards know about "the forbidden seven" and that Roy was one of them. So there was already a time when 3 FE characters weren't out of the question but time/budget constraints or whatever it was led to Roy being cut. So Chrom won't replace Ike anymore than Lucario replaced Mewtwo. Mewtwo wasn't as high a priority and ended up being cut. That is a possibility but I think it's unlikely.As long as Ike stays in, and Chrom is at least a little different from him, I feel as if most people will be neutral.
As much as I like Chrom, I would rather him only get in if Ike stayed. There's no reason to cut Ike.
I think Ike's style is unique for a lot of reasons but one is that he is one of, what I'd argue comparatively few "heavy hitters." Of the heavy hitters he's also the only one who uses a sword and one of only two who use a melee weapon at all (DeDeDe being the other). Slapping that moveset, or even elements of that moveset onto Chrom instead would seem strange. In Fire Emblem canon Chrom is supposed to be a great fighter but is never praised for his pure might to the extent that Ike is. I feel like Ike's moveset in Brawl kinda highlights the fact that he is this monster of a warrior, a concept that just wouldn't fit Chrom as well. I honesly don't see why people are so quick to jump to the conclusion that FE won't have more than 2 character. Star Fox got 3 in Brawl and it wasn't exactly a super relevant franchise at the time. Command was the most recent one as of Brawl and iirc it didn't do super amazing or anything. Awakening may have not done as amazing as some people hype it to have but it did do really really well for the series and seems like it put the series in a great place. No reason FE can't have three characters IMO.