Another cast member from Black Panther is making the jump to Avengers: Infinity War. According to IMDB, an actual article not just an updated cast list, has confirmed that Letitia Wright who will be playing T'Challa's sister Shuri will make an appearance in Infinity War.
This isn't that surprising. There was a shot in the D23 and Hall H footage that showed T'Challa standing with what looked like a bunch of Wakandian warriors at his back. He also had Bucky Barnes aka The Winter Soldier there. Danai Gurira's Okoye will also be making an appearance. The cast of Infinity War is huge so there are likely people we don't know that will show up in small cameo roles.
Summary: T'Challa, after the death of his father, the King of Wakanda, returns home to the isolated, technologically advanced African nation to succeed to the throne and take his rightful place as king.
Black Panther, directed Ryan Coogler, stars Chadwick Boseman, Michael B. Jordan, Lupita Nyong'o, Danai Gurira, and Martin Freeman. It will be released on February 16th, 2018.
Avengers: Infinity War, directed by Anthony and Joe Russo, stars Robert Downey Jr., Josh Brolin, Mark Ruffalo, Tom Hiddleston, Chris Evans, Chris Hemsworth, Jeremy Renner, Chris Pratt, Elizabeth Olsen, Sebastian Stan, Benedict Cumberbatch, Paul Bettany, Chadwick Boseman, Benedict Wong, Zoe Saldana, Karen Gillan, Vin Diesel, Dave Bautista, Pom Klementieff, Scarlett Johansson, Don Cheadle, Tom Holland, Bradley Cooper, Sean Gunn, and Anthony Mackie. It will be released on May 4th, 2018.