With Shrek 2 on course to make a cool $300 million by the end of this week, DreamWorks has stepped up production on a third film, which was already rumored as early as January this year, for a holiday 2006 release. Coming Soon says the studio has hired Peter Seaman and Jeffrey Price, the duo who wrote Jim Carrey’s Grinch picture as well as the landmark Disney/Spielberg/Zemeckis collaboration Who Framed Roger Rabbit, to pen a story which teams Shrek with King Arthur and the Knights Of The Round Table…