Moore joins David Healy and Rob Hulse alongside King who has made only two substitute appearances for Leeds so far.
Hulse is also on loan but has made an impressive start to his Elland Road career and Leeds boss Kevin Blackwell is keen on a permanent deal.
Johnson's future meanwhile rests on Sheffield United's promotion prospects. The 28-year-old is also yet to start a game for his new club and manager Neil Warnock has been linked with any number of new attacking signings.
Neither player looks to be in the future plans of Forest boss Gary Megson regardless of which division his side are in next season.