The 2018 Venom movie from Sony Pictures is shaping up. Now that Tom Hardy is ready to don the deadly symbiote suit, he's going to need someone to fight, and that villain will reportedly be Carnage. While they're not likely to go full-hero mode, a la "Agent Venom," a newer take on the character where he was a heroic super-soldier, it does seem like we'll probably at least get "Lethal Protector," the 90s Venom, who fought to protect the innocent, but more in a Punisher style "let's murder lots of people to save other people" than say Spider-Man's M.O.
The news of Carnage coming to Venom was revealed in a THR spotlight about Spider-Man: Homecoming and Sony's plans to push out into their own Spidey-centric film universe. Recent reports have been muddied, but it seems as though their Spider-Verse will be MCU-adjacent; it won't necessarily be in the MCU, but it won't directly contradict it either. The hope from Sony is also to have Tom Holland in the film (and other spin-offs) though to what extent is unknown. Carnage had been previously rumored as a villain not just for this Venom movie, but the first time a movie was put into development for the character several years ago, during the last film incarnation of Spider-Man.
Carnage, aka Cletus Kasady, debuted in 1991's Amazing Spider-Man #344, and got his symbiote a year later in #360. Unlike Eddie Brock, the primary host of Venom, Kasady has basically no moral compass. He was a psychopath and a serial killer before he got an ultra-powerful alien symbiote. He is, however, directly connected to Brock and Venom - when the Venom symbiote freed Brock from prison, his cellmate collected the symbiote's offspring for himself - yeah, that was Kasady, naturally. Colored red, Carnage's name is also his goal - to kill and wreak carnage all over the place - that's really all he cares about.
What this means for the Venom film is that we'll likely have some real bloodbaths, and some crazy symbiote-vs-symbiote fights that should be a lot of fun. No casting was reported, rumored, or suggested in the THR report. They did, however, mention Silver & Black, the female-led team-up between Silver Sable and Black Cat, as well as films in early development centered on Kraven the Hunter and Mysterio, another pair of villains.
Venom is in pre-production now for a October 5, 2018 release.