Any ideas when the prices may come down?
Two parts to that question:
1) When the Yen is not so strong, and returns to a normal range, and
2) When they are sitting on the shelves and shops need to move them.
As for #1: Since 2008, the Yen has gone from 120 to the US Dollar (and similar for the Euro, etc.) to 80 to the dollar.
That means that a $1,000 item in 2008 would now cost $1,500 in 2012. That is one reason why this lens is so expensive. If Canon get $2,300 for this now, that is equivalent to getting $1,518 in 2008. Sound familar?
For #2: Speciality shops only discount items that are not selling well.
When you have a hot item like this, the only real way to get a discount is to find a retailer that gives a "blanket" percentage off for Black Friday,, etc.
Like Dell, with 15% off all SLR camera & lenses, that type of thing. Or speciality discounters, like Buy.com, or Beach on eBay, etc.
Canon will offer rebates around Xmas, but not on the newest and hotest items.
It is a balance between having something and using it, and waiting until you can buy it a little more cheaply.
Remember that for a business the real "Cost" of a lens like this is not the sticker price. It is the "Purchase Price" minus the "Residual Value."
Take the 70-200 2.8 II, for example. It is selling used for about $1,900. If you bought that at $2,300 2 years ago, your "Net Cost of Ownership" is $400, or about $200 per year.
If you are a pro doing weddings, etc. for $5,000 per wedding, that is a small "Cost of Doing Busines." Definitely well worth the investment.
If you are an enthusiast, it really doesn't matter much if you use the lens now, or in the spring on vacation. Especially if you will not be doing a lot of work in the winter. Then again, you might have to wait 6 months to save $200. Really up to you ... how much will you use it, and how soon ...
Sorry for the "Capitalization." I just wanted to hightlight the business concepts and terms for those who make money at photography - it is a differnt way of thinking. They may or may not apply to how you do photography.