Netflix collaborated with Marvel, via their ABC production arm, to make three seasons of Daredevil and Jessica Jones apiece and two seasons apiece of the other shows, plus the event crossover mini-series, totalling thirteen seasons of television produced in just four years. Netflix co-funded the series in return for transmission rights, but ABC - owned by Disney - actually made them, and a two-year exclusivity contract was put in place so that the no-one else could make shows or movies featuring those characters after the contract ended. Today, that limitation for both Jessica Jones and The Punisher expired, returning control of the characters to Disney and Marvel Studios.
Disney's plans for the characters remains unclear. Of the group, only Daredevil and The Punisher were known to a wider audience before production started, but the shows did bring a new level of fame to the other characters, particularly Jessica Jones and Iron Fist's supporting character, Colleen Wing. Based on the contract, it appears that Marvel are free to bring the characters back with the same actors playing them, but it's less clear if they can refer to the events of the Netflix shows.
One notable issue is that, so far, Disney have kept all of their MCU output in the "family audience" category. The Netflix Marvel shows were very much not in this category, with swearing, sexual content and much more graphic violence than we've seen in the MCU to date. One possibility would be to create bring back the characters but with a more familiar MCU style or tone. Another, potentially more interesting, possibility would be to keep the adult tone and create a sort of M-rated MCU, which these characters could inhabit alongside Deadpool, whose forthcoming third film (but first under the MCU banner) has been confirmed to be an adult-oriented film. One can imagines Disney continuing these shows on Hulu, which is rumoured to be taking on a more "adult Disney" role, and on the Disney Star service internationally (a sub-channel of Disney+ featuring somewhat more adult programming).
It's also unclear what will happen to the existing shows. Netflix are currently streaming all of them as normal, but their distribution rights are no longer exclusive and they could appear elsewhere, such as on a Disney streaming service.
Rumours have circulated that Charlie Cox's Daredevil (whose rights expired much earlier) has already been seen on the set of the third Spider-Man film, currently shooting, and the MCU powers that be have already confirmed that they strongly considered portalling the Defenders in from New York City at the end of Avengers: Endgame before deciding that would be too random for people who hadn't seen the shows, indicating that Marvel Studios are well aware of the popularity of these versions of the characters and are certainly considering ways to bring them back.
Marvel is not lacking for content on Disney+ in the meantime, however, with WandaVision currently airing, soon to be followed by The Falcon and the Winter Soldier, Loki and What If...?, with Hawkeye, Ms. Marvel and She-Hulk in production and Moon Knight, Secret Invasion, Ironheart and Armor Wars in pre-production (a further series, Wakanda, has been announced but is unlikely to go into production until after Black Panther 2 is released).