About the BIG WHITES:
The last time they were updated all 4 lenses (2,8 300; 2,8 400; 4 500; 4 600) were released as IS versions together (that was back in July 1999, so more than 10 years ago!).
I´m pretty sure they´ll do it just the same this time, because there is no good reason to split that.
Have a nice wedding next week!