Still The King
This was probably a given all things considered but Marvel Studios has been known to swerve audiences before. Remember, Steve Rogers gave up the Captain America identity at the end of Civil War. Trailers for Black Panther indicate that Erik Killmonger will be challenging T’Challa’s status as king.
So when the Infinity War trailer kicks in, the first thing that we see is T’Challa giving orders. This could be a simple case of T’Challa being the most qualified person in the room, but later in the trailer we see him wearing the new suit that he gains in his solo movie. The title of Black Panther is designated for the ruler of the kingdom.