First off, let me preface by saying this question is specifically about the Christian view based on the Christian New Testament. There is still a lot of room for interpretation, but it narrows down to this:
The “dead in Christ” (οἱ νεκροὶ ἐν Χριστ ) refers to “those who are asleep” (τοὺς κοιμηθέντας; cp. 1 Thes. 4:14). The Greek phrase ἐν Χριστ means one who is incorporated into the body of Christ, i.e. a Christian.
Thus, οἱ νεκροὶ ἐν Χριστ means “Christians who have died.” Specifically, it is referring to the bodies of Christians lying in the grave, for the soul does not die upon death.
Rather, the souls/spirits of the dead Christian believers go go to heaven (or “Paradise”) upon death (cp. 2 Cor. 5:8; Luke 23:43; Phil. 1:23). This is NOT a bodily resurrection, however.
When our Lord Jesus Christ returns, the souls/spirits of dead believers will be reunited with their RESURRECTED bodies. A more perfect, immortal, imperishable and incorruptible version of the body or tabernacle you have now.
There IS a spiritual presence in Christ after death, and Paul was evidently conscious of it and said it fit him like a glove, and was too wonderful to describe. But there will come a time in the eschatological future when Christ will come again and the bodies of believers will be resurrected, and the bodies of living believers ‘translated’ into these resurrected bodies,