Could someone tell me what is involved or will be involved in changing from the integrated and a dedicated graphic card once the Raven Ridge APU,s are released?

I would like to have built a new desktop once Raven Ridge is released to replace an old laptop I am currently using. Later I would like to give the Raven Ridge system to my son and replace it with a Zen cpu. I have two MSI R9 290x's that have never been used that I would like to use in the Raven Ridge system if I am playing a game. Can I switch between the integrated and desecrate gpu's on the fly or do I need to reboot?