How many potential release dates and anniversaries have been disregard up to this point? They are nothing more than a mere indication that an opportunity is coming. I mean TF will probably get one as it is a huge launch, aside from that, I don't really think we should be looking to see when a character's debut was to see if the month is going to be the month we get a reveal. It is simply irrational.
Not sure what you're referring to.
The only game to truly be passed over for whatever reason was Pokémon.
Mario 3D world made sense because it would have had to be for a Newcomer.
Sonic Lost World got Sonic in a Nintendo Direct that focused on upcoming titles with Sonic in them.
Marth was random.
Luigi was revealed with a link to Dream Team, Olimar to Pikmin 3, Toon Link to Wind Waker HD, Zelda to ALBW...
Not every character gets a link to a new game coming out (I don't think the exact date matters really), nor does every game get one. The major ones however, I think will get one.
While Kirby Triple Deluxe may not be a big release, it is a perfect opportunity to at least reveal one of the two remaining Kirby characters, hence why I think it's going to happen, and we'll get Dedede.
The characters debut dates are probably a crap point to consider now, seeing as though it hasn't meant anything.