Next version of iOS with overhauled notifications, lock screen, Messages, Apple Music, and much more.
Mac OS X 10.4.9 (8P2111) Seeded to Developers
A number of fixes have been documented. Among those, include bugs wtih Sync Service Engine, rsync and extended attributes, .Mac Sync, Rosetta, USB Modem and caller ID, Bluetooth device pairing, USB modem busy tone detection, QC Engine, Core Graphics and HID Manager, PDFKit and MallocGuardEdges, and Automator Actions.
Meanwhile, Apple asks developers to stress certain areas for testing beyond those described in the bug fixes. These areas include Adobe Flash, bash, bind, Bonjour, Dashboard Widgets, FireWire, Fonts, gnutar, Graphics, and iChat Video Conferencing.
Apple last publicly updated Tiger (10.4.x) on September 29th, 2006.