According to Woj the Celtics are receiving 3 future 2nd round picks in the Williams deal:
Doing a bit of research the picks look like this:
2024 - both Dallas and San Antonio have already traded away their own 2024 2nd round picks ( San Antonio is already sending this pick to Boston in the Noah Vonleh trade although it is top 55 protected ) but from prior trades San Antonio has the Lakers 2nd round pick and the least favorable pick between Chicago and New Orleans.
2025 - San Antonio currently has 3 2nd round picks this year ( Chicago, Toronto and their own ) while Dallas still has their own 2nd round pick too.
2028 - San Antonio currently has 4 2nd round picks this year ( Miami, Denver - protected top 33, New Orleans and their own ) while Dallas has already traded away their own 2nd round pick.
Bottom line - who the hell knows just which picks Boston will actually end up with ????