I have been wondering the same thing. I think (and hope) there are going to be some surprises. If there are surprises then Windows 10 will get more buzz. But at the same time, a bunch of insiders might be angry that they didn't have an opportunity to test it out and give feedback. In addition to this, remember how much people freaked out over the recycle bin icon design? Think if Microsoft made a surprise UI decision for the actual release and people hate it. Then Windows 10 would have bad buzz.
If Microsoft has no surprises in the rtm release then there would be this, "nothing to see here" attitude towards it. I personally think this is worse than the possibility of people not liking the surprise elements.
I hope they surprise us with a cohesive design throughout, aka Metro 2.0 with light and dark themes. This would include visual revamps of the file explorer, device manager, the control panel (if it still exists), and even the registry. I don't think this will happen, but one can hope...