The entire gameplay content of Marvel Rivals' September 3 patch is a bug fix for Psylocke's scarf not swaying correctly on a swing in the Hellfire Bay Beach map. That's genuinely the most substantial non-cosmetic change in the whole update. Everything else is store bundles: an Ultron "B-Boy Prime" skin, X-Men '97 Season 2 bundles for Rogue and Gambit (both explicitly noted as not including their MVP animations yet, those come with a later update), a cosmetics bundle for Jubilee tied to the "Take a Seat" emote, and a free cape customization option for Cyclops.
Calling this patch thin isn't a criticism exactly, it's just an obvious tell about timing. Season 10 is confirmed for September 11 via NetEase's own roadmap, and studios almost never front-load a real balance pass or content drop the week before a season launch. You ship the skins that were already finished, patch the one bug that's been annoying people on a specific map, and save the actual news for launch day. This is a placeholder patch doing exactly what placeholder patches are supposed to do.
What Season 10 Might Actually Bring
The interesting stuff is all rumor at this point, and it's worth being clear about that distinction. Gorr the God Butcher and Nightcrawler are the two names attached to Season 10 speculation, and the sourcing here is genuinely mixed in quality. Gorr's inclusion traces back to the Season 9.5 Gallery Card's lore text, and NetEase's pattern since Season 3 has been that whoever gets teased in a Gallery Card shows up the following season, so that's about as reliable as a leak gets in this game. Nightcrawler is a shakier claim, sourced to a single prominent dataminer rather than anything from NetEase's own marketing, though he's been one of the most requested characters in the community for a while, which at least explains why the rumor has legs regardless of whether it's accurate.
If both land, the reported role split has Gorr as a Duelist and Nightcrawler as a Strategist, though again, that's speculation stacked on top of speculation with zero official confirmation behind it. I'd treat any of this as a maybe until NetEase actually puts out a trailer.
There's also chatter about a "Path to Doomsday: Infinity War" mode potentially arriving with Season 10, following up on the well-received Age of Ultron PvE mode. No details on whether it'd be PvP or PvE against the Children of Thanos, and a new map is expected at some point in Season 10 or its mid-season follow-up, but again, nothing concrete yet. For a game that's been reliably good about hitting its own roadmap dates, September 11 is the one number here I'd actually bank on.