The MCU's Phase 6 will include two new Avengers installments, and its second film, Avengers: Secret Wars, provides the franchise with the best opportunity to bring back Tobey Maguire and Andrew Garfield's Spider-Man variants. The first three phases of the MCU are known as The Infinity Saga, and 2022's San Diego Comic-Con not only announced a new slate of upcoming Marvel films but also retroactively named the MCU's next three phases The Multiverse Saga. Tobey Maguire and Andrew Garfield's previous generations of Spider-Man films were canonized in Phase 4's Spider-Man: No Way Home, and if the multiverse continues to play a major role in the MCU, their respective versions of the web-slinger are well-positioned to come back in the sixth Avengers movie.
Spider-Man: No Way Home is one of the MCU's most crowd-pleasing entries, bringing together three generations of Spider-Man films and spectacularly doing each iteration justice. While the multiverse has become a major component of the post-Infinity Saga MCU, No Way Home used it for the best kind of fan service, employing metafiction without sacrificing any earnestness. No Way Home gave each iteration of Spider-Man their moments to shine and reminded viewers why Willem Dafoe's Green Goblin and Alfred Molina's Doctor Octopus remain some of the superhero film genre's best antagonists.
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The Multiverse Saga looks to be a drastically different era for the MCU than the Infinity Saga. If Loki's portrayal of He Who Remains is any indication, Kang the Conqueror will be a far more cerebral and less brutish sort of enemy than Thanos, and he'll threaten every reality instead of just the MCU's mainstream timeline. Secret Wars may end up being the Multiverse Saga's equivalent to Avengers: Endgame, and if the film similarly brings in as many heroes as possible for a final showdown against Kang, the film would have the perfect opportunity to have Tobey Maguire and Andrew Garfield's Spider-Man variants return for the act 3 showdown. Kang the Conqueror will be a multiversal threat, so the Raimi and Marc Webb Spider-Man universes will be in as much jeopardy as Tom Holland's, and The Avengers would certainly benefit from having three Spider-Men instead of one.
As teased by the season 1 finale of Loki, Kang the Conqueror will attempt to dominate all universes, and since the Raimi and Webb Spider-Man continuities are now part of the MCU multiverse, they'll no doubt be involved in Kang's attempted conquests. Similar to the finale of Marvel's What If.? season 1, albeit on a much larger scale, Secret Wars will likely see The Avengers' ranks comprised of superheroes from across the multiverse. This might result in smaller teams like Avengers: Infinity War, with at least three sub-groups having a different Spider-Man variant, before they all coalesce in an Endgame-like finale, bringing all three Peter Parkers together again.
In one of many humorous moments in No Way Home, Tobey Maguire and Andrew Garfield's Spider-Man variants reveal that they don't have The Avengers in their realities, though ancillary material establishes that many other Marvel heroes and villains not shown in their films are part of their respective universes. Having both versions of Spider-Man join The Avengers in Secret Wars would be a crowd-pleasing payoff to this joke, in addition to allowing the three Spider-Man actors to demonstrate their excellent chemistry again. Avengers: Secret Wars could be the Multiverse Saga's version of Endgame, making it the perfect place to bring Tobey Maguire and Andrew Garfield's versions of Spider-Man back to the big screen again.