Here's wrench: what if the said person was the coach, captain, or founder of the team?
Oooo... I was gonna mention something about that, but since you like playing devil's advocate.

If the said person was only the coach, then it would be not so good, but not devastating because coaches can be replaced. If the person was the team captain, then you'll have a major blow to team morale, but still survivable because you could promote someone else. If the person was a team founder, then start looking for another team. I see a few teams where only 1 or 2 people wear all 3 of these hats, and if that's the case, then if they leave, the team is lost unless there's a strong core of "senior" team members who are willing to take over. Regardless, it would be a major detriment to the team as a whole.
The way I see it, the founder/captain's job is to give the team a goal, a focus, "a vision for the future" as it were (I know, I know, it's getting melodramatic

), and it's their job to keep the team on track. If the team founder was the one looking to jump ship, then the team may as well be dissolved.