I tend to think it won’t be in a beta per se, but rather implemented via a sever side switch at the last possible moment. How would anyone test it?
It depends on how they implement sideloading. If there are security toggles to switch on or off in Settings, then those would likely need to go through a beta process to ensure they function properly. And if the latest reports are accurate, they may be preparing to implement an approach similar to macOS app sideloading with a verified developer and unverified developer system. Verified apps would be simpler to sideload and would be from verified developers and possibly go through an app review process to verify there’s no malware in the app. This would likely be paid for by developers who want verification via a commission. Unverified apps would likely still be able to be installed, but would throw up more red flags and popups telling consumers the app is from an unverified source, hasn’t been reviewed, and may contain malware. The consumer would probably have to toggle a couple settings to allow it to install anyways, and they’d be informed of the risks of doing so. This at least what I think is the most likely way that Apple will implement sideloading, and I think they’ll probably just release it worldwide. Most developers will want their apps to be verified, and so Apple will still make a commission on those apps, but others that don’t want verification will be able to opt out, but also likely won’t be trusted by most consumers because they’re not verified. This is basically the way it is currently on macOS, but with a commission-based verification system for apps, which would also lead to greater security.