Speaking personally, I would not buy a Student license of any software, as I'm not a student and I would feel that I was being a bit dishonest.
Neither would I buy second-hand software, for the same licensing/registration concerns that you are thinking about.
But then again, I wouldn't buy Dreamweaver at all really. I'm moving away from WYSIWYG.
Could you put it off for a while and see how the market develops? I can envisage Adobe concentrating its efforts on developing DW (see Splatter's recent thread) and that may well result in an update. Version 8 would then surely drop in price to shift remaining copies, as almost always happens with old software.