Whether the eventual update on the 135L is f/2 or f/1.8 I don't really care. What would be handy is the standardization to the 77mm filter thread size plus IS. Maybe I'm not as steady as I used to be, but after using my most used lens, the 70-200 f/2.8IIis I really notice the subtle trembles with the 135 f/2 and need to be more conscious of shutter speed if I'm hand holding. Another useful option would be a tripod/monopod collar.
In any case, the current lens continues to astound me. I was late getting the 135 f/2, it was not until last year I made room in my bag for one. Out of the box it was a shocker, needing a constant +9 AFMA on all my bodies. Thank goodness for AFMA.
Another highly unethical, possibly unhealthy alternative to IS would be the use of beta-blockers http://en.wikipedia.org/wiki/Beta_blocker
as used by some athletes. Since they promote lower heart rates and reduce tremors, beta blockers have been used in professional sports where high accuracy is required, including archery, shooting, golf and snooker. Photographers too?
Beta blockers are banned by the International Olympic Committee. A recent, high-profile transgression took place in the 2008 Summer Olympics, where 50 metre pistol silver medallist and 10 metre air pistol bronze medallist Kim Jong-su tested positive for propranolol and was stripped of his medal. For similar reasons, beta blockers have also been used by stutterers and surgeons. How slow can you hand hold a 135 f/2?