An article in the The Register is reporting that after talking to Apple executive Greg Joswiak, they can confirm that OSX 10.3 (Panther) will be a 32-bit release with accommodations for 64-bit addressing (much as 10.2.7 is intended to be).
The approach will allow Apple to continue to sell a single CD-set for both 32-bit and 64-bit computers and also plays a part in the transition that will allow 64-bit CPUs (the 970 or G5 as Apple calls it) to run original 32-bit code without problems.
The system will have support for dual-mode libraries, allowing for 64-bit code and 32-bit code to take advantage of the same basic services but at different rates of speed owing to the lack of need to use the 64-bit to 32-bit bridge.
This strategy directly mirrors the 68000 to PowerPC transition strategy which kept much of the underlying operating system in 68000 code initially, which the most performance-intensive parts came over quickly, followed by the less crucial pieces. This strategy allowed Apple to have quite possibly the most successful architectural shift in the history of computing.
The Register also contrasts this situation with that of AMD, who will be waiting for the 64-bit version of Windows, since there is no announced hybrid strategy for the Windows platform as yet (I guess that's one of the advantages of controlling the hardware and the operating system).