It's generally acknowledged that as soon as The Beatles were free from the constraints of writing and recording songs that they would have to reproduce on stage, they gratefully accepted their freedom, and simply used the studio as another instrument.
When you look at the musical minds that composed those pre-Pepper songs, its not hard to see that the freedom granted to them was the keys to the proverbial kingdom, they could do whatever they wanted, limited only by technology, and more often than not, they found ways to circumvent those limits anyway.
It was neither a 'setting sun' or a 'new dawn', it was one more step on the evolutionary progress of the greatest band that has ever lived.