Symmetric powers of null motivic Euler characteristic

Let k be a field of characteristic not 2. We conjecture that if X is a quasi-projective k-variety with trivial motivic Euler characteristic, then Sym${}^n$X has trivial motivic Euler characteristic for all n. Conditional on this conjecture, we show that the Grothendieck–Witt ring admits a power structure that is compatible with the motivic Euler characteristic and the power structure on the Grothendieck ring of varieties. We then discuss how these conditional results would imply an enrichment of Göttsche’s formula for the Euler characteristics of Hilbert schemes.