Well, given the state of the US economy and the weakness of the US dollar against the Japanese Yen (and most other currencies), it had to happen. Canon have informed their USA dealer network that effective May 1st 2008 there will be a price increase to dealers. I'm sure this will then be passed along to customers. Canon Canada are following suit on May 5th.
So if you were waiting for the Canon Spring rebate program to be announced, you might not want to wait much longer, and in fact you might want to buy that lens you've been looking at before May 1st. Of course it's still possible that there will be a Spring rebate program, though rebates on the new prices may be no better than the old prices. I'd say that this announcement makes a lens rebate program for the US look somewhat less likely this spring. Not impossible, but if Canon are raising lens prices because they're not making enough money on them, it's hard to see how they could then turn around and simultaneously offer rebates. I suppose they could if they though they'd make up in volume what they lost in profit per lens, but it would be a little odd. Time will tell.
When will the retail price rise? Well, in theory it should probably be when the dealers have sold their existing stock of lenses, but my guess is that many will raise their prices sooner than that.
Canon regional companies set their own prices, so this isn't a worldwide price increase. So far it's just the USA and Canada. Canon Europe, Canon Asia etc. will set their own pricing policies.