I think it's irrelevant to pick sides on the leak considering it's not accurate.
Chorus Kids are still what will make or break it for me, Shulk proves nothing now.
Only Shulk was given the guarantee by the tipster. This pretty much means that if, for some strange reason, he isn't playable, then the leak is automatically fake. However, if Shulk is in fact confirmed, then perhaps the Chorus Kids could help strengthen he credibility of the leak again.
Actually, now that I think about it, according to the Brawl leaker, both Chrom and Robin were considered from the very beginning, with Chrom having had a slot specifically reserved for him before Awakening came out. This means that Chrom was added to the roster just slightly before Robin was. Robin never replaced Chrom; Chrom was merely deemed inadequate and boring, and that his inclusion would have been merely for the sake of meeting fan demand. Chrom was cut--not replaced but cut.
Now whether or not Chrom was even preprogrammed to be a fighter (and to what extent he was worked on) or not remains to be seen. But considering the fact that he has a full model of him as a part of Robin's Final Smash, it is very possible that Chrom's model was at the very least finished, but instead of removing him from the game altogether, they decided to repurpose him as a part of Robin's Final Smash. My guess was, a model of Chrom was finished; Sakurai couldn't figure out a way to make him stand out from Marth and Ike similarly to Robin, and instead of meeting fan expectations, decided to instead make him a part of Robin's Final Smash.
Where does Lucina come in? Well, the story pretty much speaks for itself and pretty much went as Sakurai explained it. But it was highly speculated that she was originally going to be upgraded to character DLC but made it into the Final Roster since the development team was so far ahead of schedule by that time (and according to this insider, character DLC and patches are definitely being worked on).
Now who is this tipster? I have no idea. Some of the long-term people know about the Brawl leaks far better than I do, and who it was that provided it. All I know is that the guy does not know the final roster for this game in general, and only knows some of the details that he provided while speculating most of the rest to fill in the blanks. He's a credible source, though, and believes that the gematsu leaker was a Namco Bandai employee with actual inside information. What do I think? If the gematsu leak is true, then chances are, he was either working on a completely unrelated game; was reassigned to another project (believed to be Tekken 7), or was simply not activiely involved in the game's development or marketing departments. He might be in archives, but if so, he probably would have know about Robin and Lucina before their trailer came out.
But that's off-topic. My point is, the Brawl leaker in question has a reasonable explanation that could in turn support the gematsu leak getting Chrom wrong. While it hasn't been confirmed, it is very likely that Chrom's development as a character began with the 3D modeling and may have even begun before Robin, but then was scrapped altogether when Sakurai felt there was no reason to satisfy fan demand for the sake of it. I say this because again, Chrom was made a part of Robin's Final Smash; I figured if they could help it, they would have given Robin a completely different FS that didn't involve him if Chrom never made it that far to begin with.
And I reckon someone will bring up characters like Tom Nook or the other Mega Man's to justify their possible inclusion as an argument against my theory. And trust me; while I've got nothing on those two, there may in fact be a bit more light to shed on their parts. But again, these are just my two cents on this whole Chrom situation.