I think Chavis slides into a platoon 1B/utility role in 2020. If Dalbec is good enough, it would push Devers to 1b or DH depending on JD's contract.
However, what I think will happen is the following:
Dalbec is traded
Devers stays at 3b
Chavis platoons 1b and plays some 2b/3b and corner OF