I can’t really rouse myself to be exceptionally excited about a modern-day Merlin. The legend isn’t exceptionally ripe for an update given current events as was the case with Sherlock Holmes. And we’re awash in magic-inflected pop-culture people these days. It’s a bit hard to remember what made Merlin unique other than advising King Arthur in the midst of all these vampires and wizards and werewolves and whatnot.
I always thought one of the great innovations of The Mists of Avalon was making the Merlin an office, rather than a person. It let Marion Zimmer Bradley switch aspects in and out, while making different characters accountable to a similar set of rules, and showing them succeeding or failing to meet those obligations to varying extents. I’d be curious, but doubtful, to see if a new adaptation places a similar emphasis on office and the conflict of office with personality. But if you don’t come up with a good concept, jumping Merlin into the future mostly means you get a wizard in board shorts: