I like some more roads in future, they can be flat, hilly or another mountain.
Preferably, I would like to see more dense woodland / Forest landscapery like, say, Black forest in Germany or such like, it has all the hairpins, steep sections, hills, lakes, animals, snow caps, Beer gardens, …
I think it is fair to say, that if you do several hundred kilometres a week, one does need more roads and things for change and to break up monotony.
Connect all three courses into one big landscape would be a good way to do it as well, I think.
Not for the purist but, I think a really cartoony course (remember crash team racing) would be great, we have the trikes just add some bombs, oil slicks, jumps etc.
What would be great as well is some teasers when they are building. Before the ocean boulevard extension and the mountain extension we had some road blocks.