Yes, it is true. My question to you is, "Are those who sin without repentance 'in Christ'?"Isn't it true that in Christ there is no condemnation? Why then wouldn't the sentence be eternal life in Him as well?
I am not suggesting that a disciple jumps in and out of Christ every time he sins and repents. If he is on the road to completion, he stays on the road. But if he lives in sin without repentance, then he has gotten off the road.
I am not sure about your example of the disciple who commits suicide, but I suspect that prior to the suicide his life was not right before God. For a person trusting completely in God would not commit suicide no matter what the external pressures. Thus it seems likely that one who commits suicide has gotten off the road which leads to life for a time prior to the suicidal act. The act itself is evidence that he had not repented of that condition.