Revelation 1

In the great revelation received by John, He tells us that the Savior -

"...sent and signified it by his angel unto his servant John..."  (New Testament | Revelation 1:1)

Which message came -

"....from Jesus Christ, who is the faithful witness, and the first begotten of the dead, and the prince of the kings of the earth. Unto him that loved us, and washed us from our sins in his own blood,
6 And hath made us kings and priests unto God and his Father; to him be glory and dominion for ever and ever. Amen."  (New Testament | Revelation 1:5 - 6)

Which suggests that those who receive the fulness of His atonement will be made kings and priests which also suggests kingdoms and priesthoods being then joint-heirs with Christ.

The messenger then shares an important truth -

"...he cometh with clouds; and every eye shall see him, and they also which pierced him: and all kindreds of the earth shall wail because of him. Even so, Amen."  "New Testament | Revelation 1:7)

Every eye and also them that peirced him would include the dead...the spirits of the dead then must be here on the earth.