From CBR:

According to Deadline, Lovecraft Country star Johnathan Majors has joined Ant-Man 3, possibly as the time-traveling Marvel villain. The report states Majors will play a lead role in the film. Although the studio did not comment, the report's sources indicated he is "likely" to appear as [SPOILER]Kang[/SPOILER]. Additionally, his Ant-Man 3 appearance will potentially build the character up to be a main villain in the franchise.
If that turns out to be the case, I wasn't expecting it.