Those who were being addressed by Paul were saved. This can be determined by v 6:9 in which only the saved are addressed. Every one of the “you” of 6:9 therefore must also be saved: if the group is saved then all of its members have to be too, and by that salvation, the concerns of 6:4 – 6:8, not applicable to them. Paul did not say that he expected better things of them but that he had been persuaded they already had those better things, which things, had accompanied their salvation and had eliminated falling away as a possibility.
Generally, Paul was teaching them of the inevitability and permanence of salvation, so verses 6:4 – 6:8, were intended only as additional informational to provide them with depth and deeper knowledge. They describe those who gain an intellectual awareness of Christ's salvation and His doctrines, yet nevertheless, because being unsaved, they turn back to a trust in their works over His works for justification. These, the same as those described in the following verses and which supplements that assessment, I believe:
[Luk 8:13 KJV]
13 They on the rock [are they], which, when they hear, receive the word with joy; and these have no root, which for a while believe, and in time of temptation fall away.
[Heb 10:29 KJV]
29 Of how much sorer punishment, suppose ye, shall he be thought worthy, who hath trodden under foot the Son of God, and hath counted the blood of the covenant, wherewith he was sanctified, an unholy thing, and hath done despite unto the Spirit of grace?
[2Pe 2:20-22 KJV]
20 For if after they have escaped the pollutions of the world through the knowledge of the Lord and Saviour Jesus Christ, they are again entangled therein, and overcome, the latter end is worse with them than the beginning.
21 For it had been better for them not to have known the way of righteousness, than, after they have known [it], to turn from the holy commandment delivered unto them.
22 But it is happened unto them according to the true proverb, The dog [is] turned to his own vomit again; and the sow that was washed to her wallowing in the mire.