"All Good Things," the finale of Star Trek: The Next Generation after seven seasons, followed Captain Jean-Luc Picard [Patrick Stewart] as he time-traveled through various parts of his life, some of which never happened. From his first mission at Farpoint to a dissolved marriage with Dr. Beverly Crusher [Gates McFadden], which we never got to see, the finale went by far too fast. There was a lot to pack in to wrap up seven seasons of a show that had garnered a dedicated fan following.
Initially, though, Captain Picard was going to traverse through a fourth time period, which was "Best of Both Worlds," bringing him back to the most horrid part of his life when he was assimiliated as a Borg. According to Brannon Braga [recorded in Captains' Logs The Unauthorized Complete Star Trek Voyages by Mark A. Altman and Edward Gross], the finale was going to play out part of "Best of Both Worlds" where Hugh [Jonathan Del Arco] would be aboard the Enterprise to save Captain Picard.
Becoming Locutus was an important part of Picard's history and did change him as both a man and a captain; however, Braga said "but they felt it was just too much story and we'd better have only three time periods."
"All Good Things" was an excellent finale, but including the Borg would have been an extra shot in the arm, so to speak. That was a life-changing time for Picard, and it would have brought his journey full circle. Fortunately, Star Trek: Picard managed to do that when Picard voluntarily joined with the Borg Queen in order to save his son, Jack Crusher [Edward Speleers]. Of course, if Picard were to ever return to another series, there's no doubt the Borg would make yet another return as they are forever embedded into his history and his future.