This actually occurred in my team a few months ago. The previous PM got a new job with another J&J branch and one of the principle R&D engineers got promoted to becoming PM. So in our case, it wasn’t a huge shift in that the new PM was someone who was already on the team for several years so they did not have to get up-to-speed with where the team and projects were at. The only updating that really occurred is that now we were just reporting to another person on the team. The new PM however had a huge shift in responsibilities and had to get respective training for the position. Overall, the timelines for all of our projects are still on track and there are slight differences in management styles between the old PM and the new PM but they are positive changes. So this question really depends on the situation – if we were to get a PM from outside the team, I’m sure things would have turned out a lot more different and there would have been delays in our projects.