Apple has already reported that they would be introducing their Music Download service for Windows later this year... and Forbes has already suggested that iTunes is coming to Windows.
As confirmation, Apple has posted a job listing on Monster.com for a Senior Software Engineer for iTunes for Windows:
Apple Computer is looking for a Senior Software Engineer to design and build one of our newest Consumer Applications, iTunes for Windows.
Must be possess strong skills in the areas of application design, solid API design principles, user interface engineering, and have a strong understanding of customer and workflow issues. Experience with Windows logo certification preferred. Candidate should have a history of successful large volume consumer product shipment.
Update: The same job listing is listed at https://jobs.apple.com/
