As mentioned above, Apple did speed bump and marginally improve the Mac Pro line - and the prices did drop pretty substantially from the previous models. For example the 3.2GHz model was 2899 (USD) and is now 2499 (with 3GB of additional memory). The 3.3GHz 6-core machine was 3699 and is now 2999. And, having the line refreshed a little is better than losing it altogether.
I think it's fair to say that Apple considers the Mac Pro a strategic product. Apple is primarily a consumer electronics company, but the Mac Pro gives it an important presence in the enterprise. I'm referring to medium-sized to large enterprises here, corporate and governmental, with IT departments that may be more favorably disposed to supporting iPhones and iPads if they are already supporting Apple desktops.
I believe the 2012 Mac Pro upgrade was intended to give enterprise buyers the current processor specs their internal customers were clamoring for. These purchasers don't especially need Thunderbolt or USB 3; in fact, many IT departments take a dim view of bus extenders and prefer network- to locally-attached storage. But they demand current specs, and Apple probably made a shrewd decision by giving them an incremental upgrade until a redesigned product was ready to ship. Among other things, Apple reasonably could assume that organizations which depend on custom desktop applications with OS X (or generic UNIX) dependencies would never return if they had to wait another year and went to the expense of porting their software to MS-Windows.
Not that the Mac Pro isn't profitable. I doubt Apple would keep anything in its product lineup that didn't produce significant revenue. (It bailed out of its brief, unsuccessful foray into enterprise storage, for example.) The Mac Pro's primary constituency has a high proportion of volume purchasers and, of course, margins are higher for this kind of product than for consumer electronics.
In other words, I don't think this upgrade was intended for the likes of most of us reading these forums.
Having said that, a 6-core 3.33 GHz CPU with 48 GB of 1333 MHz memory or a dual-CPU model with 12 cores and 96 GB of memory is a very powerful machine. (You need third-party memory to reach those specs; Apple's configurations only go up to 32 and 64 GB, respectively.) About the only thing missing is a disk with a fast spindle, but I'm sure the power supply could handle faster drives and, in any event, Apple as well as the third-party suppliers are pushing SSDs for high-speed local storage.
Of course, you can get equal or superior performance for less money with a machine running MS-Windows. But for those who need a UNIX-based desktop environment, or who just prefer OS X—and who don't want to wait for the 2013 redesigned model—I think the new Mac Pros are a reasonably attractive, if not spectacular, upgrade.