airport extreme

I currently have my airport extreme connected to my ISP's modem/router and the extreme is set to bridge mode. Both the extreme and the modem/router are set up as different access points, different SSID's. I am thinking about setting the ISP's modem/router to bridge mode and using the extreme to do the routing. My question is, will this disable the wifi on the modem/router and remove it from being a possible access point? If so, this is a disadvantage to changing the set up for me.