If you can ride your hybrid you can ride the road bike after cervical fusion. I know because I have C3-C6 fused as well as L2-L3 and L4-S1. I know my back is a mess but my surgeon steered me to a road bike as he wanted me off my mountain bike.
I don't know the geometry of your Madone but I have a Synapse that puts me a little more upright and shortened the stem from 120 to 80MM that also helped. However since I got it last December, I've ridden 3000 miles and the back as well as my neck have strengthened to the point I'm ready to put the original stem back on as I'm now feeling cramped.
Discuss with your surgeon if the discs involved will hinder your returning to your Madone. I would be surprised if the answer was negative. Good luck.