Something to keep in mind with the earbud formfactor is the...

Something to keep in mind with the earbud formfactor is the tendency towards feedback due to the microphones being so close to the ear canal where the output of the buds is located. This would limit the maximum amplification and hence the worst case hearing loss that is treatable, which has been deemed to be "mild to moderate", although those terms are probably not well defined. I assume having the microphones behind the ear would help with that but NUH has enough on their plate for now. Also, that would be a very competitive market.

Coincidentally, after more than a year I just got around to testing my hearing again using the app. My hearing was slightly worse so the app recalibrated my buds with the result being that the feedback whistle was very difficult to eliminate. Unless I'm mistaken, there's no option in the app to return to a previous test result. Luckily that forced me to try the "comply foam" tips instead of the relatively thin silicone ones and presto, the feedback disappeared completely and the buds were also very tolerant of the snugness of the fit in the ear canal.

But I think "mild to moderate" is about all they can safely do with the buds form factor. NUH already has the advantage of having a patent on the calibration procedure, plus high fidelity audio. The Gen4 buds will be smaller and last longer before recharging so that's very positive (I hope they can maintain the bass response and fidelity). The colour is arguably better, or at least it's well accepted in the buds market. I'd suggest adding an option in the app to return to a previous test result and trade off the hearing aid effectiveness vs the tendency to get feedback. There are some arguments against it though.