Simpson, 20, made his first Premier League appearance today in the 4-0 win over Wigan - creating Wayne Rooney's goal whilst being unlucky to get his own name on the scoresheet.
The Sunderland boss said: "If I thought there was an opportunity to bring Jonny to Sunderland, we would consider it.
"He did brilliantly for the club before, as did Danny, and it would be nice if we thought they'd come back."
Keane admitted: "It was a nightmare giving them back as they they'd settled in so well.
"But they were good professionals, hard trainers out on the pitch and ready to put everything in.
"Nothing happens until January anyway. But I know there will be a lot of teams ringing up United after Sir Alex (Ferguson) said the other week that there would be plenty going out on loan.
"His phone will be red hot at this moment in time and whether Jonny will still be there in January I really don't know, but it would be nice if we thought they'd come back."