The consensus is that Apple currently plans on announcing the details of OS X Mavericks availability and pricing during this week’s event in San Francisco. We’re hearing that, in order to kill some last-minute bugs, a quiet update has been made to the Gold Master version of Mavericks previously shipped out to developers.
Apple has pushed out updated “Gold Master” versions of its OS before, but it does so very rarely. Once an OS goes to a GM build, it’s a statement that the bits are pretty much ready for public consumption. Most of the time they do not change at all until release. At this point only bugs that could affect first-run experiences or upgraders are likely to be the cause of such a new release. We don’t know exactly what the bugs are, just that this was not a “planned” update and that some last-minute patches were the cause, but that it was also not a mistake. Apple is just getting Mavericks in ship-shape.
The Mark Gurman at 9to5Mac noticed the build number change earlier today, which went from 13A598 to 13A603 if you’re interested in that sort of thing. We had heard that a “new GM” build of Mavericks was inbound, but had assumed it would be a full-on push through Apple’s developer portal. In this case, it has apparently simply changed the build that it’s offering from its servers to the new edition. That would fit with bug fixes that could affect upgraders, as they’ll simply get the new version from the MAS.
All of this points to Apple being fairly prepared to announce Mavericks at Tuesday’s event and ship it out to customers fairly shortly thereafter.