I saw a picture of the OEM replacement back, and it is thicker than the factory one. The additional thickness is about the same as the camera hump. On the bright side, no more camera hump. But good luck finding a case.
I'm thinking Diztronic will work since it works on the S4 and Note 3. I'll find out as soon as I can get my hands on a cover but who knows when that will be.
Samsung Galaxy S5 (Verizon)
Have that case, sure doubt that there is room, it fits very well with the standard back, sure don't see any extra room in it.