Since Sony still retains the film rights to the Spider-Man property, it has the Web-Slinger's mythology covered on two fronts right now. In one corner, Tom Holland is playing Spider-Man in the Marvel Cinematic Universe, and along with being present for ensemble pieces like Captain America: Civil War and Avengers: Infinity War, this version of the arachnid-themed superhero, like his predecessors, is leading his own movies and tangling with classic adversaries from the comics. In another corner, Sony is building its own Spider-centric franchise that exists separately from the MCU, which launches this October with the release of Venom. However, apparently Sony is willing for some Avengers characters to show up in its franchise.
Sony and Marvel's cinematic partnership began following The Amazing Spider-Man 2 underperforming back in 2014. Rather than continue ahead with plans to build a cinematic universe set in the Amazing Spider-Man world, Sony decided it would start fresh once with Spider-Man more, and after being introduced in Captain America: Civil War, Tom Holland's incarnation grabbed the spotlight for himself in Spider-Man: Homecoming. Apparently this partnership is still going smoothly, and Variety reports that not only is Sony open to having some of its Spider-man characters pop up in MCU movies, the studio would also be interested in having an Avenger or two cameo in one of these Spider-movies.
What's peculiar about this is that it's already been established that contrary to what had been previously rumored, Venom will not exist in the same reality as the MCU, so it's extremely unlikely that we'd see Chris Hemsworth's Thor, Chadwick Boseman's Black Panther or any of the other existing Avengers characters appear in Sony's Spider-movies. However, perhaps that will change somewhere down the line, as Venom director Ruben Fleischer has expressed interest in seeing Spider-Man clash with the symbiote-powered Eddie Brock, as is common in the comics and what we saw in Spider-Man 3. But as an alternative, maybe Sony is interested in seeing different incarnations of the Avengers their supporting casts to participate in these Spider-movies, similar to how DC has Jared Leto playing The Joker in the DC Extended Universe and Joaquin Phoenix playing the Clown Prince of Crime in the standalone Joker movie. That way there aren't any conflicts with the respective continuities, but there are more opportunities for Marvel and Sony to share the characters.
Whether or not Marvel and Sony will work out an arrangement for Avengers characters to appear in the Spider-Man spinoff universe remains to be seen. For now, Spider-Man is still a valuable player in the MCU, and his adventures see him battling villains like Vulture and Mysterio. Sony's Spider-verse (not to be confused with the animated movie Spider-Man: Into the Spider-Verse, which is a separate thing), on the other hand, will be filled with characters like Venom, Morbius, Kraven the Hunter and Silk, all doing their own thing without Web-Head having any impact on their lives... for now.
You can get the first inkling of what Sony's Spider-franchise has to offer when Venom is released on October 5. As for the MCU, it will continue when Captain Marvel flies into theaters on March 8, 2019, followed by Avengers 4 on May 3 and Spider-Man: Far From Home on July 5.