Apple just released the Mac OS X 10.5.3 update a week ago, but seem to prepare already OS X 10.5.4 for a developer release.
AppleInsider reports that developers could already receive a pre-release as early as end of this week according to people familiar with the matter.
A new maintenance update of OS X could be necessary to accommodate the new iPhone 2.0.
More details on AppleInsider.
Don't Miss: Incredible Pokemon Gifts
Don't Miss: iPhone 8: Everything You Need to Know