The biggest thing I think that Apple could do is release an iCloud feature --> where your personal devices that are connected to the internet provide distributed computing power for a small financial reward... so that all of the "idle" computing power in the wold can be used as server power easily just by switching it "on" in iCloud (where you could also configure e.g. a whitelist of internet connections it should use to connect to this so that it doesn't end up costing you data e.g. when roaming)
I'd love it if they did generative AI stuff --- what they did with FERRET was an excellent sign, but any contribution to the general empowerment of the entire world in terms of generative AI to empower people to be able to use AI to do things they had to do manually before would be awesome.
Personally, I'd love it if Apple revolutionised the way software development works --- and specifically to do with the deployment of server based infrastructure... I love AWS, but if Apple were to make a UX for deploying databases and containerised software I feel like they would do a far better job than Amazon in terms of the UX becuase they'd definitely integrate it with something like XCode whereas AWS have to build APIs and plugins for other IDE's... but I think Apple having XCode plus a Cloud deployment system would be an incredible move (especially if they worked to support technologies like Kotlin, C, Node.js and most especially Python as well as Swift) --- but I doubt they'll go in that direction despite the fact that often App developers will still be working with Cloud services from Microsoft, Amazon or Google as serverside compute services for their apps.... If Apple did move into this area I think it could be absolutely amazing but realise it would be a big risk.
Apple Car would be great, especially if they worked with governments to provide a public network of automated Apple Cars as a public transport service.
A keynote where they declared they were deciding to lead the world in fixing climate change (rather than just leading industry) where they said they were going to provide data, strategy, jobs and huge investment to help prevent it would be an epic thing for them to do but I think that's too out of the box even for Apple.