Blue indicates that I'd be really sad to see 'em go
=SAFE IN MY EYES=
Shulk (Extremely popular in the Smash fandom, a unique fighter, and currently the sole representative of the Xenoblade series. Pretty much the only thing he has against him is the possible replacement by X's protagonist, but considering the original's popularity compared to its sequel [although admittedly X was released at a time where the general gaming consensus was shifted towards Sony], it's not likely to happen.)
Villager (Pretty much for the same reasons as Shulk, adding on the fact that Animal Crossing is a very popular series in its own right. Wouldn't mind if the City Folk look was relegated to an alternate costume with the New Leaf designs as the main costumes this time.)
Little Mac (Also a popular fighter in Smash, and it wouldn't make sense to remove a character who's all about fighting. That, and we'd lose Doc Louis. Everything is better with Doc Louis.)
Core third-parties [Mega Man, Pac-Man] (Not only would the exclusion of third-party characters in general be a step back for Smash Bros, both characters mentioned have very strong ties with Nintendo's history, with both characters cementing an important part with their NES titles. Really, the only character who has something against him is Mega Man with receiving some neglect from Capcom, but even then, Capcom would probably still be okay with another guest appearence in Smash.)
=HIGH CHANCE OF RETURNING=
Palutena (Ultimately, a big factor for her return is the decision whether custom moves are kept or removed. Otherwise, there's no real reason for a cut.)
Wii Fit Trainer (Again, there's no real reason to give the Trainer the axe [other than some controversy over their inclusion in the roster.])
Rosalina & Luma (The duo are very popular in the Smash fandom and the Mario fandom. The only real obstacle is concerns regarding the Mario series being over-represented. Otherwise, they're fine.)
Duck Hunt (Really like these two. My gut feeling of the fact that they're retro prevents these two from being on "Safe in my eyes," but that factor didn't stop ROB from returning for Smash 4, or Mr. Game & Watch to appear in all Smash games following Melee. Heck, the only reason Ice Climbers didn't make it into 4 was because the 3DS can't into processing. To help the hunting troupe's case, they've been officially stated to represent the various Nintendo accessories instead of directly representing the Famicom/NES.)
Corrin (For me, Corrin is a special case. Although I feel like they shouldn't have been in SSB4, they'll feel right at home for Smash 5. Pretty much the biggest factor is whether Fire Emblem Fates is still considered a recent game when Smash 5 goes into development. Otherwise, Corrin is a pretty unique and fun-looking character, and it'd be a shame to not have them in SSB5.)
=IFFY CHANCE OF RETURNING=
Greninja (Greninja's situation is essentially Corrin's, but magnified, as Sun & Moon can potentially be a coffin for the Ninja Pokémon. Although, it currently has the advantage of currently being the only main Water-type Pokémon in the roster (excluding Squirtle as part of the Pokémon Trainer). Even if Greninja is cut, I'd say a return as DLC is highly likely.)
Bowser Jr. (Similar to Greninja, Bowser Jr's situation is a magnified version of another character's, this time of Rosalina's. Much like her, Bowser Jr. has the problem of potentially bloating the Mario series's representation. A good chance at returning could happen if Dr. Mario is cut or relegated as an alt for Mario. Like with Greninja, a return through DLC isn't out of the question.)
Robin (Like with Corrin, a good factor in Robin's return involves the Fire Emblem series's current position at the time of Smash 5's development. On the other hand, since Robin's debut game (Fire Emblem Awakening) helped revitalize the Fire Emblem series, it's possible that they could become a mainstay.)
Secondary third-parties [Ryu, Cloud, and Bayonetta] (The fact that these characters were put in after the main game development was finished made them somewhat of an afterthought for Smash, and it's likely that they won't have high priority for the next game's third party lineup. Cloud in particular has a somewhat similar situation as Snake, as both are generally not recognized as having association with the Nintendo brand, and are usually more associated with PlayStation. I feel that these characters were added extras from the devteam's generosity, and as such I will not hold any grudge if these characters can't make it for Smash 5. However, DLC is a high probable for a return.)
=LIFE SUPPORT=
Lucina and Dark Pit (These two characters have probably drawn the most ire out of all the Smash 4 choices, and both were essentially made for a similar reason Melee got 6 clone characters: The devteam had free time to spare. When Smash 5 comes around, unless the devteam once again has free time, Lucina and Dark Pit can say goodbye to spots on the roster, as it's highly unlikely high priority will be put on them. However, as a way to make both crowds pleased, these two can be relegated to alts for Marth and Pit similarly how Alph is an alt for Olimar, so that they won't have to take roster priority, but the option to play as them is still there. In conclusion, if you really like these characters, pray.