I agree that Krystal's/the Star Fox series' relevance fading each new year definitely doesn't help Krystal's chances of being in Smash but I wouldn't be so quick to say she has no chance of being in the next game. Even if you argue that other characters have a much higher chance of getting in Smash (which is a little hard to prove 100% anyways) it comes down to Sakurai or whoever is in charge of the next entry in the series.
If he (or whoevers in charge next) sees potential in Krystal and makes them a priority then it can happen.
if you really want to know why she doesn't have much of a chance, you need to compare her to the newcomers of Smash 4
Bayonetta (
main character of a critically acclaimed game)
Bowser Jr. and the Koopalings (Secondary but from
Mario Universe, nuff said)
Cloud (a sh***y playstation character but he is still from an iconic franchise and he was the
main character in his game)
Corrin (
main character of a currently thriving series)
Dark Pit (
Last minute clone that took ZERO EFFORT/
Favoritism from creator, moving on....)
Duck Hunt (
main character of a classic retro game responsible for selling Nintendo MILLIONS of games)
Greninja (Pokemon is one of currently
biggest selling series of Nintendo and hes also a
starter pokemon)
Lucina (
Last minute clone that took ZERO EFFORT/
main character of a currently thriving series)
Little Mac (
main character of a classic retro game)
Mega Man (iconic non-nintendo character and the
main character of his series)
Mii (
Official Nintendo avatar, nuff said)
Pac-Man (iconic non-nintendo character and the
main character of his series)
Palutena (secondary character from a game the Smash Creator worked on himself. This is the only
non-clone secondary character that got in through favoritism)
Robin (
main character of a currently thriving series)
Rosalina & Luma (Secondary but from
Mario Universe, nuff said)
Ryu (
main character and face of Street Fighter II, a wildly popular fighting games series that was a staple on the Super Nintendo)
Shulk (
main character of Xenoblade Chronicles)
Villager (
main character of Animal Crossing)
Wii Fit Trainer (
main character of Wii Fit, also sold a sh** ton of games)
in what way does Krystal (a secondary character from a dying series) compare to these characters (most of whom are stars of their own game)?
this "potential" you speak of is called "favoritism". This isn't a game that suppose to fill up the roster with "who the developers like". If that was the case, characters like Ayumi Tachibana and Takamaru would have gotten in Smash a long time ago. They want to fill up the roster with Iconic Nintendo mascots that people would recognize (and if its a non-nintendo character they MUST be the main character from a popular franchise). its a game full of celebrities of the Nintendo gaming world. Krystal is essentially a D-list celebrity compared to all the newcomers in Smash 4. Just look at how many main characters they added. Mario is the only series that would warrant as much secondary characters, no questions asked. The second would be Pokemon. But from a flop series like Star Fox, that is reaching. The only reason a
non-clone secondary character like Palutena was added is because the Smash series creator himself was very hands-on in the reboot of Kid Icarus. Which included creating her recent model. Not only that but the Kid Icarus Reboot sold well (unlike Star Fox Zero). So thats like 1 out of 19 among the newcomers? Not only that, but there are way more relevant secondary characters from other series that would get in before they even consider Krystal.
the only way she would get in is if they wanted to cheaply add her in last minute as clone (without much effort on the developer's part) like Wolf/DarkPit. This would be out of extreme favoritism from the developer's part also. But that won't happen if you read about why Wolf was added over Krystal in Brawl (who was then subsequently
KICKED to the CURB in the next Smash Bros due to Star Fox growing more irrelevant)
There are also things that make her even more D-list, like the fact that she wasn't even in any recent Star Fox games nor was she apart of the iconic games of the series like
Star Fox 64 (the recent 3DS version actually sold well) or the
Original Star Fox. There is also the upcoming release of an unreleased Star Fox game that features other females. Even Katt Monroe is more relevant than Krystal lately.
i feel like the arguments for this character to be in Smash has always come from strong wishful thinking on the fan's part ("OMG THEY NEED STAFF CHARACTER AND FEMALEZ BLAHZAYBLAH") and not based on an actual likelyhood of them being in.
All I'm saying is that however unlikely some people may think it is for Krystal to return to SF or become playable in Smash, there's no denying that she has remained a very popular character over the years.
among smashboards? yes. among the general public (aka the people who make up the majority of the sales)?
no.