Cheap, lightweight, easy to use hydrofoils are a new idea. Incremental technology, granted, but still a new thing.
I think for kites the leading edge tube is due for a new idea. The inside of inflatable stand up paddle boards are bridled, so when inflated they don't form a cylinder but a board shape.
This could be used to make an inflatable kite shaped like a foil kite.
New electronics on the kite. Gathering data on kite speed and orientation, wind speed etc.
It'd be nice to get rid of the bladders, integrate bladder into the cloth.
More opensource plans for DIY kites.