I'm thinking of upgrading my bike, which has a Sora 9-speed system on it (50/34 chainset). The upgrade is for esthetic reasons - i simply like the look of the internal cable routing. That being said, it is not an absolutely essential upgrade, and if it costs too much I will not do it. 

My plan is to buy the new Shimano 105 5800 11-speed cassette, shifters and chain. I understand that the 11-speed chain is thinner than a 9-speed. Does this mean that I also have to buy a new crankset to replace my 50/34 Shimano Compact FC-R345 Octalink?