I think that changing members sometimes does good to bands. I mean... Wes left limpbizkit, ok, but now they have a magnificent album out! Same with P.O.D.! So, unless a band breaks up, i think the well-known phrase "what does not kill you, makes you stronger" works.
I reckon if Joe leaves to do King Rat, I reckon thats when Chester will go have surgery on his hernia thing. Leaving plenty of time to recover and Joe and Chaz to be back for album number 3