The way the recall was worded ("In response to recently reported cases of the new Galaxy Note 7, we conducted a thorough investigation and found a battery cell issue"), it sounds to me like the issues is with one cell of the battery.
The way these batteries are made, there's a paper-thin (actually thinner) separator between the cells, and if this separator gets punctured (physically or electrically), then the battery will go up in flames. (see this video - although they use a knife, it doesn't take that much destructive force to cause this to happen)
https://www.youtube.com/watch?v=AAZ62tUtc0w
If a cell separator is the issue, then this theoretically could happen anytime. I only charge wirelessly, and would "like to think" that I'm safer, but I don't think so.