I've been wondering a lot lately about Paul's warning, given more than once in more than one letter, about not inheriting the Kingdom. Is this a warning of a lost reward aimed at believers who never do put off the old man and don't cooperate with being grown into the image of Christ? Indulging the flesh does always seem to be the context of the warning so it's possible...unbelievers inherit nothing but wrath and can do nothing that's not of the flesh anyway...so saying they have no inheritance in the Kingdom because of such behaviors would go without saying. It's a given because they won't enter anyway.
Yet, if this thesis is true, the believer is still crucified with Christ, buried, raised, ascended and seated in Him. Plus, declared dead to all condemning law. Plus, granted His very righteousness. Plus, forgiven all trespasses. So salvation, justification, glorification, etc, are secured in Christ.
But rewards can be gained or lost. I really wonder if inheriting the Kingdom (not entering it, since the believer is already transferred there in the King) is one such reward.
The Apostle Paul is speaking of conduct unbecoming one declared righteous in Christ.
One who's conversation (manner of life) is in Heaven; who has the inheritance. He is contrasting that with their carrying on in the manner of the lost.
They already have the inheritance and are to match their conduct to its citizenship, "as becometh saints" Rom. 16:2.
Colossians 1:
12. Giving thanks unto the Father, which hath made us meet to be partakers of the inheritance of the saints in light:
13. Who hath delivered us from the power of darkness, and hath translated us into the kingdom of his dear Son:
Galatians 5:
16. This I say then, Walk in the Spirit, and ye shall not fulfil the lust of the flesh.
17. For the flesh lusteth against the Spirit, and the Spirit against the flesh: and these are contrary
the one to the other: so that ye cannot do the things that ye would.
18. But if ye be led of the Spirit, ye are not under the law.
19. Now the works of the flesh are manifest, which are these; adultery, fornication, uncleanness, lasciviousness,
20. Idolatry, witchcraft, hatred, variance, emulations, wrath, strife, seditions, heresies,
21. Envyings, murders, drunkenness, revellings, and such like: of the which I tell you before, as I have also told you in time past, that they which do such things shall not inherit the kingdom of God.
See also 1 Cor. 6: 5-12; Eph. 2:1-7; Eph. 5:1-8, etc.