Preview at WWDC likely in June, followed by September launch.
Mac OS X Leopard 10.5 GM Candidate Build (9A581)
Based on our sources, Apple had not quite reached that goal, but today released an internal "GM candidate build" which could represent the final version of Mac OS X Leopard, if no other issues are found.
Apple has been working against the clock to get Leopard duplicated and shipped for an October release. October 26th has been noted to be planned ship date, and Apple has already been training support staff in anticipation of its release.
The Build number for the latest GM candidate is said to be 9A581.