Whatever you are smoking, I want some. Exchange Online isn't going anywhere and I doubt deprecating EWS is going to matter because where are those customers go

Whatever you are smoking, I want some. Exchange Online isn't going anywhere and I doubt deprecating EWS is going to matter because where are those customers going to go? GMail where they would have to completely change how they do business and use their APIs instead? Nope, they will just bite the bullet and rewrite everything to use Graph API instead. As for Microsoft wanting EMail Data for mining vs not hosting, check out the MSFT revenue. It's not in Advertising space that's for sure.