Star Trek: Discovery season 4 can bring back the Klingons, but it should be Star Trek: The Next Generation's version of the warrior race. This would fix the problems CBS's flagship Star Trek series ran into when it reimagined the Klingons in Star Trek: Discovery season 1. Since Discovery is now set in the 32nd century, it would make sense to bring back the Klingons fans already love but Captain Michael Burnham (Sonequa Martin-Green) and her crew haven't met in their most popular iteration.
The fan ire that met Star Trek: Discovery season 1's revamped Klingons seemed to forget that the race has been rebooted a couple of times since Star Trek: The Original Series introduced them in the 1960s. TOS' Klingons were much more human but Star Trek: The Motion Picture completely changed them physically and behaviorally. TNG and Star Trek: Deep Space Nine thoroughly explored Klingon culture, history, and mythology through the lens of Worf (Michael Dorn), and this made the Klingons more popular than ever. DS9's "Trials and Tribble-lations" slyly winked at how different TOS's Klingons were to Worf, and Star Trek: Enterprise's prequel series attempted to explain this conundrum via the Augment Virus, which didn't quite please the fandom as a whole. So, the Klingons' canon was already a mess, but Star Trek: Discovery seemed to make matters worse by making the Klingons even more alien, despite the show set in the same 23rd-century era as TOS.
Star Trek: Discovery jumping 930 years into the future was the ideal fix to the series' many prequel problems, but season 3 outright avoided the issue of the Klingons during Burnham's first year in the 32nd century. However, in season 4, Star Trek: Discovery is poised to reintroduce the Klingons, and, ideally, it should be TNG's version that Burnham and the Disco's crew encounter next. It's a perfect time to have the Klingons return since their whereabouts have been a mystery after The Burn altered the galaxy and caused the collapse of the United Federation of Planets. But now that Burnham and Discovery have restored the Federation's dilithium supply, which is gradually restoring warp travel and long-range communications across the galaxy, it's only natural that the Klingons would come back into the scene - possibly as antagonists to Starfleet once more.
Of course, there's plenty of room for the Klingons to have evolved since fans last saw them in the late 24th century so they can be somewhat different, and even contain elements of Discovery's iteration of Klingons, while still remaining the recognizable TNG version of the aliens. Star Trek: Discovery's Klingons were maligned by fans, but, to be fair, their Klingons were also soulful and filled with depth. Indeed, Discovery produced two memorable Klingon characters in High Chancellor L'Rell (Mary Chieffo) and Voq, who was surgically transformed into Lt. Ash Tyler (Shazad Latif).
Meanwhile, Burnham and her crew have only met the version of the Klingons from Star Trek: Discovery season 1 so meeting TNG's Klingons would be akin to a First Contact for the Disco. Burnham might also be surprised to learn that the Klingons and the Federation were staunch allies in the 24th century and fought side-by-side during DS9's Dominion War. It would certainly be fun to see Discovery's crew playing catch-up to the complex history of the Klingons since they last saw them in 2258. Star Trek: Discovery could certainly rise to the challenge of creating new TNG-style Klingons as complex and interesting as Gowron (Robert O'Reilly) and General Martok (J.G. Hertzler).
However, the Klingons resurfacing as rivals to or even outright enemies of the resurgent Federation in 3189 would be best. It would be fascinating to explore how Klingon society was forced to change in the post-Burn galaxy and whether they reverted back to being a race of conquerors. Perhaps the Klingons are threatened by how the Federation is now rising to be the dominant power in the Alpha Quadrant and in control of the galaxy's new dilithium supply. But what's most important is Captain Burnham and the crew of Star Trek: Discovery coming face-to-face with the Klingons in their most popular, bloodwine-drinking, bat'leth-swinging TNG-inspired form, which would give Trekkers what they're clamoring for.