One of the initial tip-offs that Apple had indeed quietly updated the Mac Pro yesterday was the addition of a small "New" tag to the Mac Pro listing on the main page of the Apple online store, a tag that was also added to the MacBook Air and MacBook Pro listings due to their updates.
Apple's Mac lineup on June 11 with "New" tags on MacBook Air, MacBook Pro, and Mac Pro
Apple appears to have had a change of heart today, however, perhaps deciding that the extremely minor update to the Mac Pro may not be worth promoting to a significant degree and removing the "New" label from the high-profile listings of its Mac products in the store.
Apple's Mac lineup on June 12 with "New" tags only on MacBook Air and MacBook Pro
Apple is reportedly still investing in its desktop lines, with the company reportedly planning significant enhancements to the iMac and Mac Pro sometime next year.