Aston Villa striker Darren Bent is set to make a loan move to Brighton in the next 48 hours, according to Sky sources.
Juan Cala wants to find 'another club ASAP' and believes Cardiff have acted without respect towards him.
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.