This rumor, via CBM, has comeback because it appears Avengers: Age of Ultron has hired an extras casting coordinator in South Africa. This will definitely get the rumor mill working at full steam for theories and speculation that Black Panther will finally make his big screen appearance.
Whether Black Panther will show up in Avengers: Age of Ultron or not remains to be seen but, in the comic book universe, his kingdom is Wakanda in Africa. So it's an easy thing to begin speculating about. Not to mention Marvel Studios president Kevin Feige has spoke publicly several times about wanting to get Black Panther onto the big screen at some point in the future.
However, there is no confirmation by Marvel Studios, Disney or any other large trade websites about filming in South Africa so until more information about the potential of filming there should be treated as rumor. Especially since IMDb is not the most reliable source until a studio or trade site can confirm info first.
Stay tuned because Wakanda is definitely an important puzzle piece in the Marvel Cinematic Universe since, again per the comic universe, Wakanda is a big source of vibranium and perhaps Ultron is after vibranium to build himself a