Kelly, 25, returned late from a trip home to Australia and was dropped for Saturday's Qualifiers loss to Leigh.
Peacock said talks are "ongoing" about resolving the disciplinary issue and whether he will face London on Sunday.
Asked if Kelly had a future at the club next season, Peacock told BBC's Super League Show: "It's all down to Albert. At the moment, it's all up in the air."
Kelly has been an influential figure for Hull KR since joining at the start of 2015, helping the Robins to last season's Challenge Cup final.
A win over Leigh would have put Rovers second in the Qualifiers table, but a 25-18 home defeat left them fourth and battling to preserve their Super League status for next season.
Former England captain Peacock continued: "It was a difficult decision to make because at times Albert has played very well for us this year, and just the enormity of the game.
"But you show compassion and give someone time to go home, and they stay longer and hamper your preparation for potentially the biggest game of our year so far - you have to draw a line in the sand somewhere.
"It's disappointing for me, but his actions end up letting the club, the players and the fans down because he wants to do something outside what we're trying to do as a club."
Meanwhile, stand-off Maurice Blair will miss the game against London after being allowed to return home to Australia to attend the funeral of his brother.
Hull KR head of rugby Jamie Peacock is unsure if half-back Albert Kelly will remain at the club in 2017.