Falcon showed up in Ant-Man, Thor cameoed in Doctor Strange, the list goes on.
That being said, the MCU has a habit of letting other superheroes cameo in a movie led by a different protagonist.
Next year, Black Panther will finally lead his own solo adventure in the Marvel Cinematic Universe, so everyone who liked T’Challa in Captain America: Civil War will be able to see him kick ass on his own.
So even though T’Challa will be the one under the spotlight on February 16, 2018, there’s a good chance one of his fellow costumed crimefighters will pop in for a moment or two.