Scientists estimate that human cells, on average, are replaced every 7-10 years — a fun fact, particularly for those who choose to interpret it as an impetus for change and escaping the past.
Though the real answer is no, you aren't a new person every seven years because some things don't fundamentally change and different types of cells are replaced at different rates, the symbolism is inescapable.
We can apply a turbo-charged version of this idea to NBA teams — entities that are far more complex than one simple human body. Teams often under go dramatic changes many times even during the course of one season, making them unpredictable and diminishing the value of cumulative results.