As far as I know, he's only signed through this year. Here's the details of his contract.
Dontrelle Willis p
1 year/$4.35M (2006), plus $0.2M in incentives
re-signed 1/06 (avoided arbitration)
$4.35M for 2006 paid as follows:
$0.2M up front,
$2.65M during 2006 season
$1.5M deferred
$0.2M in incentives
$50,000 for 35 g
$100,000 for Cy Young award
$25,000 each for All-Star selection & Silver Slugger award
2006 contract is record for first-time arbitration-eligible starting pitcher
1 year/$0.3785M (2005), re-signed 2/05
1 year/$0.3535M (2004), re-signed 3/04 (split contract paying $188,891 in minors)
agent: Matt Sosnick
ML service: 2.143