There are many versions of the iconic starship Enterprise in Star Trek, and upcoming series Star Trek: Picard is set to potentially answer which version is in service in the late 24th century, twenty years after Star Trek: Nemesis. Star Trek's fictional history covers three centuries, and in each era at least one vessel dubbed Enterprise has played a pivotal role in Starfleet's mission.
So far, there have been seven major Starfleet vessels named Enterprise; the most closely associated with Jean-Luc Picard is the Enterprise-D, which he commanded for seven seasons on Star Trek: The Next Generation. The Enterprise-D met its end in Star Trek: Generations, the first movie to feature the TNG crew. For the remaining three Next Generation films, Picard and the crew helmed the Enterprise-E, the most technically advanced starship in the Federation's arsenal up to that point. The events of Star Trek: Picard reportedly pick up twenty years after the events of Star Trek: Nemesis, the last film to feature the TNG crew, and which ended with the Enterprise-E undergoing a major refit.
While there have certainly been plenty of Enterprises in Star Trek over the years, Starfleet vessels actually tend to stay in service for many years. James Kirk's Constitution-class Enterprise was in service for three decades, though it had at least two major overhauls along the way. The Enterprise-B was an Excelsior-class starship that had its maiden voyage at the beginning of Generations. It was launched in 2293, and Excelsior-class vessels were still in service almost a hundred years later.
When it was introduced at the beginning of The Next Generation, the Galaxy-class Enterprise-D was framed as a technological leap forward, the jewel in Starfleet's crown. Despite the destruction of the Enterprise-D, the Galaxy-vessel remained one of the fleet's heavy hitters all the way into the 2370s. But for the fleet flagship, Picard and the TNG crew were given the Enterprise-E, Starfleet's first Sovereign-class vessel, equipped with enough firepower to take on heavy hitters like the Borg and the Dominion.
There's, of course, the real world consideration of whether or not the producers of the Picard series may want to design a new Enterprise for the series. Creating an unfamiliar Enterprise-F could be an effective way of communicating Picard's existential distance from Starfleet. But barring something truly catastrophic, there's no reason the Enterprise-E shouldn't still be in service when Star Trek: Picard begins. The ship was state-of-the-art two decades ago, and Starfleet tends to get more than twenty years of life out of their major vessels. Barring an offscreen war or a massive accident, the Enterprise-E should probably still be around.
Her captain, of course, will not be Jean-Luc Picard. By the beginning of the new series, Picard has retired from Starfleet, spending his days tending to his family vineyard. We still don't know why Picard walked away from the organization that so defined his life, only that he suffered a great loss, possibly tied to the destruction of Romulus. It wouldn't really make sense for any of the other TNG cast to be the ship's new captain other than Data, who at the moment is still technically dead.
No matter which version of the iconic Enterprise shows up in Star Trek: Picard, it will be a very different vessel from when audiences last saw it. Even if it does indeed turn out to be the Enterprise-E, it will be a completely new ship without Jean-Luc Picard in the captain's chair.