Tasks that have the outSR property in their Context parameter will return features in the specified spatial reference.
Spatial Reference syntax:"outSR": {"wkid" : <wkid>}
wkid is the well-known ID of a spatial reference. See Using spatial references for supported spatial references and their IDs.
Spatial Reference example (GCS_WGS_1984)
"outSR": {"wkid": 4326}