The latest word I heard from SD was that a vote by the manufactureres was going to take place this winter to decide what to do about the open class. SD said they were voting to change the 800cc class to 600cc for 2006. My understanding was that the other mfgrs were voting the same way. My source at SD felt the 440 would probably follow in a year or two.
If you are waiting to buy a 440 racer with a 600 in it, you'll have to wait longer. Maybe a couple more years.