Disjunctive-binding first-order logic decidability conjecture

Let $db$ denote the disjunctive-binding fragment of first-order logic, whose binding-form grammar permits disjunctions but not conjunctions. Its satisfiability problem asks whether a sentence has a model.

Disjunctive-binding decidability conjecture. The fragment $db$ enjoys a decidable satisfiability problem.

The source proves that this fragment does not have the finite-model property, but conjectures that satisfiability is nevertheless decidable. The motivation given is that standard undecidability proofs appear to require both conjunctions and disjunctions of binding forms; no resolution is supplied.