Dang, neuro, you beat me to it.
Yes, their pattern suggests that they like to put a month or two between rebate cycles, so I would guess that more likely than not they'll have a spring or summer rebate that covers lenses like the 50L, but that's only based on rebate history.
They seem to spend more time in rebate season than not, but I think that's standard practice. Post high prices and have constant sales to give the illusion of a good deal. And since they're enforcing minimum pricing now, they have complete control over us.