Real Madrid are considering activating their purchase option to sign on-loan Manchester United striker Javier Hernandez.
Lukas Podolski wants to return to Arsenal when his loan expires at Inter Milan, according to manager Roberto Mancini.
The duo joined the Foxes at the start of November and will now remain with the npower Championship promotion challengers until January 2 2013.
Lingard played for United's Under-21 side on Monday and helped create Federico Macheda's goal in the 1-1 draw at Southampton before he was sent-off for handling the ball on the line. The 19-year-old has made four appearances for Leicester.
However, Keane's spell at the King Power Stadium was curtailed by a hamstring injury he sustained making his debut for the Foxes against Bolton on November 6.
The England Under-19 centre-back will link-up with Nigel Pearson's squad when he reaches full fitness.