i am currently looking for the same. I managed to get IKEA Tradfri managed from RPi via CoAP and now I am looking on how to plug this into Hyperion.
I noticed that we can dump output to file where it can be picked up by another process and then transfer it to bulbs using CoAP commands.
However I am having problems with color definition as IKEA is accepting colors in XY format and output from Hyperion is in RGB...