Dan Wakin has the scoop at the Times. This detail jumped out at me:
The article goes on to report one silver lining: Fabio Luisi, who is consistently leading the house's most satisfying performances of late, will be covering most of Levine's schedule. Needless to say, that doesn't mitigate the worries of Levine's many fans. Aback injury of that nature on top of stenosis is very serious.
The timing of the news – the day after Labor Day, and with just under three weeks to opening night, talk among opera fans and music biz denizens will focus more on speculation concerning Levine's future than on the bold and promising productions being offered up.