Surprisingly good bokeh for 70-200 f4L is on the 6D, wide open at f4. Can't wait to try out my new 135L for portraits!
The 70-200 is a fabulous lens for the price. F/4 at 200mm and 6 feet from the subject is .79 inches. That is a pretty small depth of field, and so bokeh is pretty nice.
People sometimes don't realize how small depth of field becomes with a telephoto even though the aperture doesn't seem all that large. The depth of field is actually LARGER at that distance with the 85mm f/1.2L wide open.