While this all does bode pretty well for K. Rool, I can't say with all certainty that Gematsu is dead. Sure, they were totally wrong about Chrom, but they got literally everyone else. It's possible they have some outdated information, and Sakurai decided to go with Robin instead of Chrom after they had gotten their info.
Sakurai confirmed the roster was defined before development began. The only thing that justifies Robin over Chrom but Chrom still being at one point considered would be if Chrom was considered but quickly dropped in favor of Robin all before the game even began development. Which means this information was EXTREMELY outdated, or just flat-out wrong.
Getting "everyone else" isn't much of an advantage. Look at what he got. Wii Fit Trainer and "Mii Fighter." Everything else was either completely expected already, or inaccurate (Animal Crossing Guy, Pokemon from X/Y).
I don't think he just "made a mistake" on Chrom. He was also dead set sure that Shulk was going to be revealed today. I checked the release dates of both Fire Emblem and F-Zero games. TODAY is the anniversary of F-Zero X's release, and Fire Emblem had TWO games released this week. Fire Emblem: Monsho No Nazo on DS was released July 15, 2010 in Japan and Fire Emblem: Blazing Sword was released in Europe on July 16th.
There's no way that's a mere coincidence. Sakurai never once planned to announce Shulk today, although he very well could've set the plan in motion to have Shulk teased so everyone believed it was Shulk, then drop the bombshell and kill what remained in the Gematsu leak once and for all.
Yes, the remaining info could be accurate. But a blatant and cruel disconfirmation like this destroys any credibility it had and opens the floodgates wide open for more and more character speculation. I applaud Sakurai for this show, and although the disconfirmation was cruel, I also applaud Chrom's sacrifice to save the Smash Bros. roster.