In sociology, a team with a purpose, no matter what it’s doing, goes through 4 phases; forming, storming, norming and performing. The team should be creating it’s own norms in order to perform, and fight for the norms during storming.
Hyper productivity level for a Scrum team is way beyond performing. It’s actually the place where team basically has no trust issues and team is in a high level state of self-organisation.
The question usually raises at this point; what happens if we change the team formation?, e.g. a new person has joined in? An ordinary Scrum team at the performing level might need to get new norms because the teams has some new elements and the nature of chemistry needs equilibrium.
On the other hand, if the team is in the hyper productive stage, the same situation will be observed, if the team is not working in that level for too long. If the team is in the hyper productive level for a long time, then the affect of the new person won’t cause the team to go down to a lower level. This actually is about the morphogenic fields (as Jeff Sutherland states at his google speech) which says, if a culture is strong in some place, the adaptation period for the joiners will be shorter. I think, same is true for those teams not in hyper productive but performing level. So, if the joiner is a change agent and try to change the culture inside the team, the joiner will be changing quickly at the opposite direction or the team’s direction.
In conclusion, the culture created inside a team is very strong as compared to individuals. The seeds should be planted very carefully during the earlier phases otherwise it can cause the team become a monster that eats everything for breakfast. (Ref: Peter Drucker, Culture eats strategy for breakfast)