Apple has been rumored to be targeting Mac OS X 10.5 Leopard's release on October 26th.  More evidence of that comes from Apple's own online store.  While Mac OS X 10.5 Leopard is not yet available for pre-order from Apple, Apple still sells Mac OS X 10.4 (Tiger).  If you try to order Tiger now, the estimated ship date is coincidentally also October 26th, 2007.

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Quick Update: Apple has updated their store and changed the ship date for Tiger back to "Within 24 hours".

ON: Mac OS X 10.5 Leopard’s release via @jpenabickley