According to Nortel the DMM is supposed to be out Q1 2010, but who knows at this point.
I have gotten two answers from them on the upgrade. One person said the gutswap will leave it as a 400, but it will have 5.0 software. The other said what we mentioned in this post, that it will become a 450 on R5.
I will post any definitely answer I get from Nortel or if I do one of the upgrade beforehand.