Question:
Does John 15:6 mean that if one does not bear fruit that he will be cast forth, or cut off from this life?

Answer:
The Lord says in John 15:6: “If a man abide not in Me, he is cast forth as a branch, and is withered; and men gather them, and cast them into the fire, and they are burned.”

The Lord is speaking in verses 1-5 of His disciples, true believers. In verse 6 He is speaking of a mere professor: the graft into the vine did not take. It was only attached to the vine outwardly nag a branch,” and so cannot bear fruit for God. Such a one is fit only to be burned in the Lake of Fire.
In verses 1 & 2 we see that even true believers who aren’t bearing fruit might have to be “taken away” in death as some were in the assembly at Corinth (1 Corinthians 11:30).
The Lord purges His branches so they will bring forth more fruit. The new growth of the grapevine must be cut back or it won’t bear fruit. So we must be pruned of self so we can bear the fruit of the Spirit (Galatians 5:22, 23).