We have it on good word that Mac OS X 10.4.10 has been seeded to developers. It is build 8R2205 for Intel, 8R205 for PowerPC.
Mac OS X 10.4.9 was first seeded to developers in December 2006 and released to the public in March 2007.
As an aside, this confirms that subversion number 10 is the natural successor to subversion number 9 in Apple's numbering scheme. While many thought this pattern was obvious, previous Mac OS X releases have never reached subversion 10.