I hope they keep the switch allowing you to disable Apple Intelligence.
I already have Siri limited to manual activation only. If they force all of this into Siri and I can't prevent AI models from actually installing their gubby hands all over the phone then that's it for me.
>no way to adjust what data gets cached or when it gets purged aside from rebooting
Unfortunately the only current ways to pull this off is to either artificially move the current time years forward so it hits a time gate and dumps the cached files, or use enough space on your iPhone to force it to dump the useless cached files then delete whatever you used to take up space temporarily.