Will Type 1 Diabetes be widely considered cured by the end of 2040?
Resolution will be based on whether a treatment arises for Type 1 Diabetes which reverses the damaged beta cells, or replaces them, or through some other mechanism the body is able to resume natural insulin production. This treatment must be approved by the FDA in the USA and must be widely available. I personally have T1D and will be very actively monitoring research and new treatments to judge the resolution criteria.
Cures will not include automated insulin delivery systems (which currently exist, such as my own setup of a Dexcom G6 + an OmniPod 5). A cure must allow production of insulin in the body, and any ongoing medicine required for this cure cannot include insulin or any wearable devices (insulin pumps, CGMs, etc).
Pancreatic transplants do not count as cures unless major transplant breakthroughs arise and synthetic / lab-grown pancreases are widely available. The cure cannot lead to significantly worse symptoms or quality of life than classical insulin therapy.