He is speculated to be in SSB4. Like Ike did for the generation before the Wii, Krom could represent the 3DS branch of the franchise and use his sword in a different style than the other Fire Emblem characters from past entries in Smash.
A. Sword Slash (similarly to Link)
<-A-> Sliding Strike
A ^ Skyward Strike (like Lynn)
A V Ground Stab
B. Light Blade: Krom's blade glows and unleashes a slash of light. This move is chargable.
<-B-> Running Stab: Self Explanitory
B ^ Light Glory: Krom charges light into his blade and stabs it upward, sending a bolt of light from it.
B V Light Spreader: Krom sends two waves of light in either direction to damage the opponent.
Final Smash: Light Prismal Streak