1. Tier-1 server suppliers like HPE plan to make a Centriq server. For customers to stick their neck out and start porting critical software to a new architecture, they have to believe that there's going to be a refresh next year, and the year after that. Some adventurous customers will be ready to explore this territory but the critical mass won't move until they see momentum shift that way.
HPE and Qualcomm each have a popular brand and big budgets that can sustain a slow ramp of a couple generations of these products before they start to see major adoption.
2. What else is different this time is the ever-increasing popularity of: open source software, linux, containerization, python, golang, node/JS, Java, C#, etc. Redhat announced at SC this year that they will offer a supported ARM release. That means that all of the above will Just Work.