Ellen at the UNC Press blog is worried that digital-only catalogs are just the first step:
I doubt this is the case precisely because there are people like Ellen around to worry about something like that. The nice thing about the book industry is that, unlike other industries, it's still dominated by people who use and love the things they make. It's a lot more likely that an auto industry CEO will cancel some car he doesn't view as the most profitable possible than bibliophile publishers are going to stop making books because they see a little more revenue in it.
In any event, I don't think printed books are going to be a losing proposition anytime soon. The market is going to give people the product they want: most readers don't buy or otherwise consume catalogs, so publishers are going to digitize away. By contrast, we're seeing a lot of "keep the book" sentiment among consumers, leading me to believe that publishers are going to view printed books as desirable for some time.