Originally Posted by
OshkoshBiker
I have the same bike with the stock wheels. Trek told me the hub is 8/9 speed compatible only.
Well, actually it's 8/9/10-speed compatible but that doesn't help the OP if he really want to go to 11-speed.
alcjphil phrased it extremely well; "The upgrade from 9 speed to 11 speed is not incremental." It can and will be expensive.