It almost certainly depends on the company. Consider General Electic's microwave oven firmware and hydroelectric control station software. Both might actually s

It almost certainly depends on the company. Consider General Electic's microwave oven firmware and hydroelectric control station software. Both might actually share some code. Maybe they both use GEEventLoop or GEHardwareButton or something. But there's no reason to be concerned about having different versions in production at once. I don't think there's a universal answer to your question.