Magical Beasts abound.
Regardless of what age he is when the story starts, there's huge potential here for Fantastic Beasts to be its own great series, connected to but not directly related to Harry Potter. In addition to giving us some background information on Newt, everything within Fantastic Beasts indicates that he has always had a deep appreciation for magical beasts, including their history in the wizarding world, their varying degrees of dangerousness, and how a witch or wizard can defend themselves against them. Newt doesn't go into detail as to how he came to learn about each individual creature, though he does cite references to encounters from other wizards, but that's all the more reason to consider the potential of this story. Did Newt ever encounter the shroud-like smothering Lethifold, or keep a Krup as a pet? Has he ever visited a dragon reservation to study the various species of winged, fire-breathing beasts? Has he ever heard the dying scream of a jobberknoll, a creature that, when it dies, lets out a long scream made up of every sound it has ever heard, regurgitated backwards? And what are his experiences with Grindylows and Merpeople? Fantastic Beasts is brimming with fantastic beasts, many of which were not featured in the Harry Potter films.
Go ahead and thumb through Fantastic Beasts and note the detail Rowling has put into it, including the occasional amusing anecdote or reference included in the footnotes. If one thing is clear, it's the limitless potential in the Harry Potter world. One of the best aspects of the Harry Potter series was the world in which the story was set, which Rowling often described in colorful detail. But most of that was related to Harry's story. From what was referenced in her previous books, it was always fairly evident that the wizarding world had a rich and thrilling history, and Harry Potter really only scratched the surface of it. Rowling knows this world better than anyone, which makes her the perfect person to do the screenplay. Newt Scamander's story seems like an exciting place to start exploring different times and places within the world with a character we know very little about. It's a whole new story, but set in a world we know and love.
In terms of potential for crossover with the Harry Potter world, we know his career overlaps with Dumbledore's tenure at Hogwarts, and Voldemort's original rise to power. Newt retired in 1979, which was at the point when Voldemort would have been at his strongest, and just a couple of years away from being thwarted by a baby. Whether or not Newt's retirement had anything to do with Voldemort, we couldn't say, but it seems worth noting the time frame. So while we are dealing with a non-prequel/sequel, it's worth considering that the later part of this character's life overlaps with the prequel-space of the Harry Potter series.
Is Newt Scamander the next Harry Potter?
What it comes down to for me, as a die-hard fan of the Harry Potter books, is optimism, particularly in the fact that Rowling is writing the screenplay. Granted, that's somewhat new territory for her, but the fact that she's directly involved in this adaptation makes me hope that we're going to be in for another great story set in the same world many of us spent years visiting and revisiting. Will Newt be the next Harry Potter? I don't even know if we should be intent on drawing that kind of comparison, since Newt presumably has a completely different story and background than the boy destined to face off against one of the most deadly wizards in the history of this world. Newt has his own story to be told, but that's all the more reason to be excited by this project, since there are so many blanks for Rowling to fill in. And on quality, the story could prove to be just as thrilling, entertaining and engaging on its own merits.
With all of the above said, I say, bring on the dragons! Bring on the Sphinxes and Sea Serpents, Salamanders and Shrakes. Throw in some Manticores, Doxies, Pixies and Phoenixes. And tell me a story of a young wizard whose job it is to travel the world seeking out these exciting magical creatures.