I had the same thing happen to me with Alitalia once, and though I didn't end up buying the ticket, both the airline and Expedia claimed the seat would be business. If you examine the fare rules through Expedia, you'll see that the fare type is:

INDUSTRY FARE TYPE - BR - BUSINESS CLASS RESTRICTED

And the fare basis is ISALEU2. So, this looks to me like a discounted business class sale. I _think_ what happens is that Expedia's computers doesn't really know what to do with this "I" fare, so it's inconsistent.

In case I'm wrong, I would suggest emailing Expedia. That way, you have a paper trail if they try to assign you a seat in economy and you want to cancel.