I'd like to replace a Shimano 105 5800 11-28 cassette on one of my bikes (CAADX 2016) with a CS-HG800-11 11-34 to get a wider range of gears.
My rear derailleur is Ultegra RD-6800-SS, which can't take a cassette this big. I am thinking of replacing it with RD-R8000-GS (current generation of Ultegra, medium cage, takes up to 34t).
Are there any potential issues to be aware of with this combo (6800 shifter, R8000 derailleur, CS-HG800-11 cassette)?
P.S. The bike has a 44/34T cyclocross crankset. Both the front shifter and the derailleurs are Ultegra 6800 (11-speed). I plan to keep all of that as-is.