Speculation and rumor. Really, really hesitant about putting up a more solid link, but rumors are rumors. My advice? Tread cautiously, my friends, because if this rumor is true, kudos are in effect for Marvel and also these four words:
It’s about damned time!
I love T’challa and if this is true then I am happy (can we have him in for Avengers 2 as well? I need some Steve and T’challa friendship).