It's interesting that there is no mention in the letter of resolving the training ban....only that it will be mitigated. That doesn't suggest the author/company is actually interested in resolving the issues!
I believe your assertions on upgrade rate are correct. However PC is correct on one statement - yes time to upgrade will steadily reduce from the current rate. But that's because the current rate is 10 per year - so if we do 11 next year, that is a reduction from 50 years to upgrade to 45 - then if it is 12 in 2020 that will further reduce from 45 years to just over 40years.
