Following on from this question, where it's established that druids do not count as 'Shapechangers' for the purposes of effects which relate to them, if a druid is in beast form using wild shape and is affected by the Moonbeam spell, failing his/her save, the following occurs:
When a creature enters the spell's area for the first time on a turn or starts its turn there, it is engulfed in ghostly flames that cause searing pain, and it must make a Constitution saving throw. It takes 2d10 radiant damage on a failed save, or half as much damage on a successful one.
A shapechanger makes its saving throw with disadvantage. If it fails, it also instantly reverts to its original form and can't assume a different form until it leaves the spell's light.
It's not clear to me whether this bolded section means any creature that fails its save reverts to its original form, or only shapechangers revert to their original form.