Star Trek: Picard season 2 will reveal an alternate timeline where Jean-Luc Picard is not only back in Starfleet but is a high-ranking flag officer. Thanks to the return of Q (John de Lance), Star Trek: Picard season 2 will be a time travel adventure where the omnipotent being promises to explore the "road not taken", not just for Jean-Luc but for the motley crew he has assembled as well.
Of course, Jean-Luc Picard is no stranger to time travel and he's had numerous jaunts backward into the past throughout Star Trek: The Next Generation, whether it was in San Francisco in the 19th century or facing three different points in the timeline threatening to collapse reality, as seen in TNG's series finale, "All Good Things", which also involved Q. Star Trek: First Contact, where Picard led the USS Enterprise-E to stop the Borg from assimilating Earth in the 21st century, is his other most famous time travel adventure. But in Star Trek: Picard, Q finds an older Jean-Luc who still has regrets about key decisions he made in his past. Although Star Trek: Picard season 1 made him feel "useful" by saving the galaxy once more, there's still one major choice Jean-Luc made that eats away at his very soul, which is likely what led Q to seek his old friend, "Mon Capitaine", out once more.
Star Trek: Picard season 2's trailer reveals that Q will show Jean-Luc and his crew alternate realities in a compelling series of "what if" scenarios. Picard's own lost timeline sees him back in uniform at Starfleet, and Jean-Luc has 8 pips on his collar, which denotes the rank of Admiral. After 18 years as Captain of the Enterprise, Picard was promoted to Admiral before he quit Starfleet in protest over the Federation abandoning the Romulan supernova rescue mission in 2385. But in season 2's alternative reality, he's not only Admiral Picard again but he appears to be Commander-in-Chief of Starfleet, hence the 8 pips on his uniform. This would make sense as the "road not taken" for Picard in season 2 as the Admiral was likely in line for the top job running the entire fleet had he not voluntarily walked away from his decades-long Starfleet career.
It was clear in Star Trek: Picard season 1 that Jean-Luc desperately missed serving in Starfleet and that he yearned to be back in space. But Jean-Luc was also bitter and angry at Starfleet, which he felt had lost his way. Turning his back on Starfleet was Jean-Luc's way of teaching them a lesson, but it actually backfired and left Picard out in the cold, far removed from the action as he ended up living the life he never wanted running his family's vineyard in La Barre, France. Until Dahj (Isa Briones) appeared at his door and provoked Picard's season 1 mission to save her synthetic twin sister Soji and the galaxy, Jean-Luc was mired in his own regrets for 14 years.
Therefore, an alternate reality where Admiral Picard now runs Starfleet and sets it on a better path would indeed be Jean-Luc's not-so-secret heart's desire, and the omnipotent Q would certainly exploit this. Jean-Luc has few other regrets in his eventful life and Star Trek: Picard season 1 allowed him to deal with another huge "road not taken" by allowing him to say goodbye to the late Commander Data (Brent Spiner), which he was denied in Star Trek: Nemesis. Jean-Luc also got to reconcile his feelings about the Borg after realizing that they can be reclaimed in great numbers in Star Trek: Picard season 1.
An alternative timeline where Admiral Picard becomes the Commander-in-Chief of Starfleet would let Jean-Luc address his final two grievances: quitting the service and allowing the Federation to abandon the Romulan rescue mission in 2385. If this is indeed the "road not taken" Q shows Jean-Luc, the question for Star Trek: Picard season 2 will be whether the Admiral will be able to give up his heart's desire as easily as he turned his back on having a family in the Nexus in Star Trek Generations.