I previously voted for 135/2L but received my 70-200IS II and I must say it is definitely an amazing lense ! Razor sharp everywhere, better than my 100-400L with a 2xIII (slower AF but better IQ and better IS), definitely a must have lense ! 135/2L still have more wow IQ, but 70-200IS II is not far and so versatile !
I think it is a little soon to go with the II super-tele, my fav 300 2.8 IS was not on list so I put 70-300L instead, also use and like 24 1.4 II and 100L a lot.