I would never sell my 135 L as it is my first choice for outdoor portraits on full frame. I sold my 70-200 f/2.8 IS II since it rarely got used due to the weight and my preference for primes (I mainly shoot portraits). I picked up a 70-200 f/4 IS for the times I need the versatility of a zoom lens. On the other hand, I rarely use ultra wide lenses, so my preference for the 135 L. YMMV.
my 70-200 doesn't get a ton of use either (albeit more than the 135), but when I do need it, there is no other lens in my kit that can even come close to replacing it. Between the zoom range, IS, and 200mm reach, I find it very difficult to beat. A few days after I first bought the 70-200, I told myself this will probably be the one lens I never sell...3yrs later I still feel the same way. Nothing else I own even comes close to taking it's place for when I need reach and/or versatility.
I already have the For Sale thread written...maybe I'll bring myself to actually post it tonight