So... Yeah, Chrom. Honestly, I'm open to the idea, but, here's my take on the whole thing.
I believe it was in an interview with Famitsu that Masahiro Sakurai stated that Chrom was considered but ultimately rejected because, I'm I'm likely paraphrasing things here, Sakurai did not want a character who was just another swordsman. This is rather confusing, since Lucina is not only in the game, but is almost a direct clone of Marth. So why would he be against including Chrom with the logic that he'd just be another swordsman, when you include Lucina, who IS just another swordsman (er, woman), whose moveset is lifted from Marth to boot?
Well, I think it might have something to do with variety, as well as Sakurai's logic on including clone characters. If Sakurai IS going to include a character whose moveset is similar to another character's, they'd better have something else going for them. For example, I've seen many a complaint about Shulk being in the game, because he, too, is another swordsman. However, I feel that not only is Shulk different, in that his sword is drastically different from any sword seen previously, but Shulk also uses his Monado Arts to add a lot of strategic value to the character. Same goes to Robin, who is also technically a swordsman, but there's more of an emphasis on his tomes and magic then his swordplay. When it came to Chrom, I guess Sakurai didn't see that much going for him that made him that much different then, say, Marth or Ike. Now, I HAVE seen a number of people suggest ideas that would make him different, such as switching between a lance and such, but I guess those ideas never occurred to Sakurai. I'll touch up on this more in a minute.
For now, let's move on to Lucina. So, why include her of she's going to play almost identically to Marth. Well, again, according to Famitsu... Well, actually, some of this information may be inaccurate, and feel free to correct me on any of this, but from what I recall, there was originally supposed to be another character that didn't quite make the cut and, not wanting to sacrifice the roster size, Sakurai game Lucina her own slot on the roster. Coupled with that is the fact that Lucina was originally intended to be an alternate costume for Marth, but Sakurai and his team picked on little details that made her different, likely things like size, the shape of her version of the Falchion, etc. According to Sakurai if a character who's similar to another character has enough differences going for him/her that make him/her unique, they'll be their own character, which is probably why Dr. Mario and Dark Pit are supposedly going to be playable as well.
Given the backlash against this idea, I don't know if it was wise to do it at all. Really, I kind of wish I knew just went on behind the scenes during development just know exactly why they committed to this. Not that I don't like the idea, but clearly a lot of people don't anyway. Regardless, she's playable now, and we're just going to have to deal with it.
But what does that mean for Chrom? Well, like I said, it IS technically possible to make Chrom a unique character while still being a swordsman. But if he WERE to be a DLC character, well, that just begs some questions... The most important of which is, what's going to happen to Robin's Final Smash? Will it stay the same? Will it change whenever Chrom's playing? Will it permanently change to another character if Chrom becomes playable? If so, then who? Who else would fit Robin's "Double" Final Smash? I feel like not just anyone can replace Chrom, given how close they are in Fire Emblem: Awakening, and since Lucina's already playable, well... Also, DLC characters, in general, are tricky to deal with, because they change the meta of the game. Making a new character for, say, Mario Kart isn't the same as making one for a fighting game, especially one with a competitive scene like Super Smash Bros. When you create a new character, you have to think about how they'll fight against other characters, and you also have to think about how those other characters are going to fight against them. You have to make sure the character is well-balanced enough so that he/she/it doesn't overpower other characters, but also doesn't match-up poorly against the other characters either. There are a lot more factors to this then just tossing together a character to appease the fans. In fact, it would be easily just to create the character while developing the main game then to just wait until after the game's released to think about adding him/her/it...
But who knows, maybe Sakurai DOES have DLC characters in mind, and is working on them as we speak... We might not know about them until after the Wii U version is released, though. For now, I'll just say this: Chrom as a DLC character, I'm totally fine with that... but I'm not getting my hopes up about it, either. It would be cool, but I kind of doubt it all the same.