Three reasons why the opening scene leak doesn't matter.
Three reasons why the leak / rumor of Tobey Spider-Man dying in the opening act won't matter:
There is a rumor that in addition to Tobey fighting to defend his universe, Doc Ock and Green Goblin will also fight Magneto while Deadpool and Wolverine fight Spider-Man. This means that the Earth-96283 is not the original Earth-96283 from the Raimi trilogy, it is the branched timeline created in NWH when Ock and Goblin were pulled into the MCU timeline. They were returned to Tobey's universe alive and cured, therefore making a branched timeline where they wouldn't have died as villains. There is also another rumor that Tobey will actually have an Iron Spider suit instead of his original suit, which Octavius helped Peter to create after having been cured, his tentacles were subdued by Tom earlier using the iron tech. This explains why the leaked set photos of Tobey don't have him in costume, but in the CGI gear instead. So basically, everyone in that universe is just a variant of the actual Earth-96283, therefore there is no actual significance to Tobey or anyone in that universe dying. The original Earth-96283 is either still intact or can just be written off as having been already pruned, Goblin and Doc Ock are dead in the original timeline.
It's Disney, Secret Wars will end with undoing everything that Doom could and possibly will inflict on anything and anyone, just like how the snap in Infinity War was completely undone with no consequences.
Even then, everything is going to be reset and rebooted after Secret Wars so anything not in the MCU is screwed either way lol