Specialized palliative care teams improve outcomes for the steadily growing population of people living with serious illness. However, few studies have examined whether the specialty palliative care workforce can meet the growing demand for its services. We used 2018 clinician survey data to model risk factors associated with palliative care clinicians leaving the field early, and we then projected physician numbers from 2019 to 2059 under four scenarios. Our modeling revealed an impending "workforce valley," with declining physician numbers that will not recover to the current level until 2045, absent policy change. However, sustained growth in the number of fellowship positions over ten years could reverse the worsening workforce shortage. There is an immediate need for policies that support high-value, team-based palliative care through expansion in all segments of the specialty palliative care workforce, combined with payment reform to encourage the deployment of sustainable teams.