So, look up the specs of the derailleurs.

RD-6800-SS
Capacity 33T
FD Max Difference, 16T
Rear Cassette, Max rear sprocket, 28T

You have: 16T on the FD.
32-11 + 16 = 37T

So, you have about 4 teeth too many on the rear sprocket, both for total capacity, as well as max sprocket size.

Looking at the 6800-GS.,
Total Capacity: 37T,
Low sprocket, rear, 28T to 32T

Sounds just about perfect for your bike.

Looking at the RD-R8000-SS.,
Rear large sprocket, 25T to 30T
Capacity: 35%

RD-R8000-GS,
Rear large sprocket, 28 to 34T
Capacity: 39T

So, you're quite a bit outside the specs for the RD-6800-SS. If you tried it, you'd likely have issues with cross-chaining, depending on how you configured it the chain, and perhaps rubbing on the 32T rear sprocket.

You could drop down to a 28T or smaller rear cassette and get it to work.

The RD-R8000-SS rear derailleur is closer, but you're still just slightly beyond the specs for that. Again, it might work, but you could have issues with cross-chaining, and rubbing on that rear large sprocket.

Of course, the other option is to install the Dura Ace 11/23 rear cassette, and get rid of those pie-plate cassettes.