updated 04:52 pm EST, Thu December 27, 2012
Suggests naming scheme taking after Final Cut
A book listing on Amazon.ca suggests that Apple is at work on a new version of Aperture, AppleInsider remarks. The listing is titled "Apple Aperture X - under NDA: A Workflow Guide for Digital Photographers," and mentions a March 1st release date. It appears to be a placeholder though, as the description talks about Aperture 3, and "under NDA" is a reference to a non-disclosure agreement that Amazon and/or the publisher appear to have broken.
If the book title is right, it would point to Apple following the same naming scheme it used when updating Final Cut Pro last year. What a new version of Aperture might feature is uncertain, but Apple has lost significant ground to Adobe Lightroom, which has been on a continuous update cycle since its launch and is already at v4.x. Aperture 3 was released in early 2010.