This paper investigates factorial W * -bundles and their ultraproducts. More precisely, a W * -bundle is factorial if the von Neumann algebras associated to its fibers are all factors. Let M be the tracial ultraproduct of a family of factorial W * -bundles over compact Hausdorff spaces with finite, uniformly bounded covering dimensions. We prove that in this case the set of limit traces in M is weak * -dense in the trace space T (M). This in particular entails that M is factorial. We also provide, on the other hand, an example of ultraproduct of factorial W * -bundles which is not factorial. Finally, we obtain some results of model-theoretic nature: if A and B are exact, Z-stable C *algebras, or if they both have strict comparison, then A ≡ B implies that T (A) is Bauer if and only if T (B) is. If moreover both T (A) and T (B) are Bauer simplices and second countable, then the sets of extreme traces ∂eT (A) and ∂eT (B) have the same covering dimension.