I had the same notice on Friday after placing my order on Monday evening.
I waited until a couple of hours after the keynote at wwdc. The store had shut down so you couldn't order anything until after the keynote anyway. I had been waiting for the new model and saw the new air with the new haswell chips. Configured my order and thought nothing more until late yesterday evening when I had the same message appear on my order as leolabs.
I spoke to the customer service person this morning and was told nothing useful. Now I have an updated dispatch day. It's not too much of a delay - a couple of days - but annoying considering I placed my order for the new model only hours after it's release. If they've got massive order backlogs because of the launch of the new product they should say so and if they've screwed up my order they should say so and apologise, but they shouldn't use this message when it doesn't make sense - they're not replacing anything- I order the new product! it just worries people about whether they'll get their orders or not!
It sounds like you did the same leolabs.
Anyway, hopefully we'll both get the products we ordered without too much delay.