It's also a strategic move by Marvel to get people to see the Black Panther movie. He's a fan favorite of the comic book fans, but he's not that popular to the general audience. Civil War did a good job introducing the character, now we have to wait two years before the solo flick. So they will have to really push the BP movie with cameos from other characters for the general audience to see the film.
All I know is he better show back up in the MCU before his debut solo flick.