Wishfull thinking, but I doubt it will happen anytime soon. The 400 is so reliable/easy to maintain and the DRZ has a reputation to uphold, so I don't think they will risk that.
Two separate Suzuki dealerships have confirmed to me that Suzuki is already testing the DRZ450, to be released as an 06'. I would suspect that they will continue to produce the DRZ400, as it is a very popular, reliable bike that targets a slightly different market than the WR, CRF-X, and EXC.