TBH I never thought SNK would even have a chance. But at least I'd be way more excited for one of their inclusions than say.. from Bamco.
Here's the Top 5 I would like to see (in no particular order).
Nakoruru:
Uses a dagger and a bird to attack. She could probably also use the bird to hover like Peach/Daisy do. She could easily implement attacks from already present fighters, plus a few new ones, but the end result would be more than the sum of these parts.
Mai Shiranui:
Immediately recognizeable, and a fan favorite to many. Another ninja, but a very unique one at that, since she uses a fan to attack, and fire attacks.
Haohamaru:
Great characater with even greater hair style. Finally a katana-wielder in the roster (we could argue that Eight uses a katana... but I dunno, looks like a chinese broadsword to me). My only worry here is that I feel Mii Swordsman feels like a mini spoof of Haohamaru. Other than that, this guy was basically Neo Geo's mascot for a while.
Athena:
An extremely likeable character with fun abilities. Naturally they'd go for the KoF version because I don't think the Arcade Athena is that popular.
The biggest draw to this character HAS to be having 8 DIFFERENT alt. costumes. Because she basically gets a new outfit every KoF, so Sakurai would definitely want to represent that.
Marco:
A bit tied with Terry, but Terry is the predictable choice. And while I don't know a whole lot about Metal Slug, I feel he'll have a really unique moveset. (Also, probably having alts for other Metal Slug characters?).
EDIT:
If we do get a KOF character, I would love the trailer to reflect all the KOF fanfare (because it's usually a huge tournament event in the games, and it's usually a particular character/boss/subboss that gives out the invitation, so... huge opportunity here).