But it does have EVERYTHING to do with REMAININING IN CHRIST, IN WHOM is our JUSTIFICATION and SANCTIFICATION.
What you and many do not understand is that "in Christ" has a variety of applications in the New Testament and each must be interpreted by its immediate context to understand the appropriate application.
For example there are several different ways to be "in Christ:
1. We are CHOSEN "in him" before the foundation of the world - Eph. 1:4
This is "in Christ" by PURPOSE before we were born. The elect have been Abiding "in him" in this sense for thousands of years before they were born into this world and thus had no decision on their part for thousands of years to determine abiding or not abiding in him.
2. We are CREATED "in Christ Jesus" by new birth - Eph. 2:10
This is solely "his workmanship" that is beyond the power of the human will to effect (Jn. 1:13). In John 15:3 they had already been cleansed by the Word or regenerated or metaphorically their bodies had already been cleansed (Jn. 13) but only their "feet" and "hands" needed daily cleansing (Jn. 15:4-14).
3. We are SEATED "in Christ Jesus" in heavenly places right now - Eph. 2:6
This is by LEGAL POSITION or justification by faith
4. We are BAPTIZED "into Christ" - Gal. 3:27
This refers to a one time act whereby we are FIGURATIVELY and PUBLICLY "put on" Christ by baptism in the likeness of his death, burial and resurrection (Rom. 6:4-5).
5. We are METAPHORICALLY placed "in Christ" in regard to church membership as the local visible body of Christ is the metaphorical body of Christ in a local community such as Corinth - 1 Cor. 12:27 (note "ye" not "we").
6. We are EXPERIENTIALLY "in Christ" by our WALK - Col. 2:6
To "walk in the Spirit" (Gal. 5:25) is to be filled with the Spirit (Eph. 5:18) and it is to put on the new man so that Christ is made manifest in our DAILY life and is the same as crucifying the flesh DAILY. At all times we are either walking after the flesh or after the Spirit. Abiding in him in this sense is an off and on EXPERIENCE. It is in this manner we expereince the blessing of salvation here and now as we walk "in him" - Col. 2:6. This has to do with our TEMPORAL state here and now (1 Cor. 3:14-15) and temporal judgements here and now as well as rewards later. This is what John 15 refers to. John 15 does not refer to being "chosen in him" nor "created in Christ" nor "baptized into Christ" nor "in Christ" by justification/legally/positionally but rather our daily experiential walk "in him."
But those who failed to abide in Christ and bear fruit are taken out of the Vine by the Father and cast out as a branch and burned. You are ignoring the clear reading of the passage and reading something else into it which isnt' there.
There are judgements by God that have nothing to do with determining entrance into heaven (1 Cor. 3:14-15). There are TEMPORAL judgements by God here and now under the chastening hand of God. Lot was judged in this manner by God through men. He suffered the "loss" of his testimony before men and the "loss" of many experiential blessings of God so that his heart was vexed but his soul was still saved.
No, the consequences of not abiding in Christ and producing fruit is for that branch to be TAKEN OUT OF THE VINE (CHRIST) and BURNED. That has nothing to do with the 'temporal condemnation by man'. To NOT BE IN CHRIST is to NOT BE SAVED.
No, you are daily walking "in him" and out of him as no one walks "in him" consistently and constantly and thus perfectly without sin (1 Jn. 1:8-10). However, the natural maintenance of that walk is to immediately repent and have fellowship restored. However, that is not the case always. For example David must have gone nearly nine months in unrepentance and during that time he was immersed in misery (Psa. 32:2-4). There is a sin unto physical death whereby God takes the child home as a temporal judgement when they continue in willful sin and do not respond to chastening.