It seems like flight characteristics are pretty much covered. It seems the only way to REALLY make strides in flight characteristics would be what is happening now...going further.
My prediction and wish for new discs would have to be improvements in how a disc feels in the hand. Many people will disagree with me on this, but I love the way the Quarter K feels in my hand. As a result of this, I feel much more consistant with this disc which is why it has replaced the Beast in my bag. It's not any longer than other drivers (IMHO), it doesn't really fly any differently, but the feel of the disc is what makes this one valuable.
If someone could make a Cobra-like disc that doesn't have such a sharp lip, I'd love it.
Another prediction, and one I do NOT wish for is an abundance of "specialty" discs. Thumber discs, thumbers that spiral 5 times, designated distance rollers, designated cut rollers, tall grass rollers, bare ground rollers, 100' approach, 110' approach, etc.
I don't need a disc to do fly/roll differently, I just need flights that I'm getting now with a more comfortable, predictable release.
OK, one more I'd like to see, but would go against the current disc standards of accessablility to anyone. How 'bout custom fit putters? These could be molded to the hand for an absolutely perfect fit. Like a bowling ball drilled specifically for your hand or ski boots molded specifically for your feet, a custom fit putter could prove to improve accuracy.