they were cancelled because HSTY allegedly wanted to put the resources towards expanding the range of 2000-level units, rather than providing all these 3000 courses that were only taken by a small minority of students. something like that, anyway. it's also part of the uni's (or maybe artsfac's, can't remember) push to 'streamline progression' through majors by not having different courses at different levels with different prerequisites, but instead just providing senior units all at the same level and simply requiring a certain number of them for the major.
HSTY2679 is meant to be a replacement for the research element of the 3000 courses. tough luck if you don't specialise in australian history, though.