Since I’ve been diagnosed 47 years ago, they’ve been saying that the cure is 5 years away. What they don’t tell us is that it is ALWAYS years away! 
Seriously, though, I don’t think any of those estimates were ever made in bad faith. I think we are finding that the more we learn, the more we know how little we know. For one reason or another, potential cures in animal models don’t carry over to humans. The past few decades have been GREAT for diabetic mice!
I’m most optimistic about the work of Denise Faustman. Here is an article about her work. It’s been a haul and has not gone the way I’d hoped, but I think it is still promising, albeit more that five years away…