The surprise announcement of an expansion was made at a press conference following an executive committee meeting, with Motsepe saying it was evidence of his organisation's "commitment to world-class football with the best African players from all over the world returning to compete on the continent."
But he did not explain how the format will work with four extra teams, nor when it would be implemented.
The last four Cup of Nations finals have all had 24 participants, increased from 16 in 2019.
Motsepe insisted the 2027 finals would go ahead as planned in Kenya, Tanzania and Uganda.
There is to be another Cup of Nations tournament in 2028, after which the continent's showpiece event will be held every four years.
CAF is to introduce a Nations League annually from 2029 with a 16-team final tournament held every two years, he added.
"We have to stop this thing of African fixtures not being predictable, consistent and reliable. We must develop football in East Africa, which is an area of much potential," Motsepe said.
He also announced regulation changes that he said would strengthen trust and confidence in its referees, VAR operators and judicial bodies, but did not give concrete details.
African football's governing body has been battling a crisis of confidence after its Appeal Board stripped Senegal of the Cup of Nations title in a decision that has been met with widespread derision.
Senegal were ruled to have forfeited the final in Rabat on January 18 after walking off the pitch in protest at a potentially decisive penalty awarded to Morocco. They returned and scored a goal in extra time to win the game 1-0. The decision is being challenged at the Court of Arbitration for Sport and if Senegal win back their title, it will be a further blow to CAF's credibility.
"CAF has taken extensive legal advice from top African and international football lawyers and experts, to ensure that the CAF statutes and regulations adhere to and implement global football best practices, on and off the field," Motsepe said in a statement on Sunday.
"This is important for the respect, integrity and credibility of African referees, VAR operators and the CAF Disciplinary Board and Appeal Board.
"CAF is working with FIFA for the ongoing training of African referees, VAR operators and match commissioners so that they are as good as the best in the world... CAF has made significant progress over the past five years in implementing governance, ethics, transparency and managerial best practices,” the CAF president added.
More precise details on the changes and how they would avoid a repeat of the Cup of Nations final controversy were not given by Motsepe, who earlier this month admitted his organisation was struggling with perceptions about its integrity.