Nkosi arrived at Ezenkosi at the beginning of the 2018/19 season from parent club Pirates, where he only made 10 appearances in the 2017/18 campaign.
What followed was a long-term knee injury that delayed his progress with the National First Division side, and he only returned to the pitch in November last year.
Tthe former Free State Stars hitman wants to play Absa Premiership football next season, either with Pirates or Cosmos.
"We don't know yet, we will discuss it when the season ends because talking anything positive or negative now might have an impact on him," Sono tells snl24.com/kickoff.
"So we prefer to wait until the season ends, then we will decide. He is a good person, a very good person, good player. But we haven't decided yet.
"Immediately after the last game we will decide whether we keep him or we don't keep him."
Cosmos are 12th on the NFD table and have very little chance of reaching the promotion playoffs this season. They are six points above the relegation zone.