What would bring twin-gun mounts back to destroyers

Will dual-barrel deck guns become more common on future destroyers?

Only if threat conditions worsen enough, and governments take them seriously enough, to justify heavier conventional armament.

The return of twin mounts is a political forecast as well as a technical one. A heavier gun fit becomes more plausible when governments judge future conflict to be severe and political leaders treat the danger seriously. Armament therefore reflects threat assessment and procurement choices as much as naval engineering.