I am familiar with the story of Ñāṇavīra Thera, and while I deeply appreciate his work, esp. on 12 Nidanas, which for me is a good evidence that he indeed could have been a stream-enterer, I feel that his suicide was a very unfortunate outcome of the bad karma he created in the past. This karma, in its turn, came from a chain of negative mind states that evidently spanned multiple lives.
While, generally speaking, anyone can decide to commit suicide, a decision to do so is more likely to be made by someone who 1) is not afraid to die, 2) sees the pain associated with continuing to live, 3) has aversion to pain, and 4) does not see much value in continuing to live.
Because stream-enterer is beyond the illusion of self, s\he is not afraid of death. Because s\he clearly sees conditions that lead to arising of pain, s\he sees the pain associated with life. Because s\he is not yet beyond sukha-and-dukkha, s\he can still have aversion to pain. What remains is #4.
The value in continuing to live falls into two categories: the value for oneself and the value for others. Because stream-enterer is beyond the illusion of self, the only reason to carry on this particular life would be the value he or she thinks s\he could bring for others.
In Mahayana tradition, the first idea you learn, right after the basic concepts of Samsara, Nirvana, Enlightenment, and Karma -- is the high ideal of compassion. By this ideal, if I don't have a reason to live for myself, if I can alleviate suffering of even one dog, it is worth to continue living, let alone if I can help one human, let alone if I can help multiple people, let alone if I can teach Sat-Dharma.
So, while stream-entry refers to the same basic milestone that is known as First Bhumi in Mahayana, a Bodhisattva of First Bhumi would only choose to die if doing so would greatly benefit more people than he could benefit by e.g. teaching Dharma. For example, participating in the repair of Fukushima nuclear station could be a great way to die for someone who has no reason to live but does not have an aptitude to teach Dharma. There are many other ways to help humanity and die a hero whose name will be on a monument, instead of becoming a topic of regret that no one wants to mention.