Auditions have been announced for Eclipse. This comes from Acting 411 the same place that announced the New Moon auditions:
"Summit Entertainment has started preparing the sequel New Moon, based on Stephenie Meyer's second book in the series, and to contain costs, the studio is filming the third book, Eclipse, back to back using the same new director. On Sunday, December 7th, Summit Entertainment confirmed that Catherine Hardwicke will not direct the films New Moon or Eclipse. Filming begins on New Moon in March, 2009, and will continue right through completion of Eclipse."
Go here to see the audition info.