Apple seems to be making no progress whatsoever on AI so it's unclear what role they would place in this new type of marketplace. Google/Gemini certainly seems to be lightyears ahead of them. Claude is also making demonstrable progress on creating a marketplace. ChatGPT not so much, their MCP servers are currently buried in the Connectors section of Settings menu.
I think what's so cool about this is because MCP is an open standard, anybody can incorporate an MCP client into their own software and give users the ability to mix and match MCP servers. There will undoubtedly be commercial winners in the end, but this time it could be a much wider marketplace than two incumbents.