What could bring trainable missile launchers back?

Could arm launchers give smaller frigates and corvettes useful air-defense missiles without VLS?

They could, but absent sustained development they are unlikely to return until operations repeatedly expose the inability to reload VLS magazines.

Trainable missile launchers are considered potentially useful for smaller frigates and corvettes. Reloading their separate magazines is the attraction. The gap in sustained launcher development is presented as a barrier to a return. A future pattern of regularly exhausting VLS ammunition could create the pressure to revisit the idea, but an early revival is not expected.