This is interesting, I don't think this is the full solution we seek yet but maybe it's coming!
I saw this article today, saying Evernote's migration to Google Cloud Platform, and away from their own backend servers, is almost complete:
https://www.engadget.com/2017/02/09/evernote-google-cloud-platform/
You may see that one of the points in that article is it says the platform will supply "Encryption at rest", automatically. That feature is summarized here:
https://cloud.google.com/security/encryption-at-rest/
So I am not an expert on this, but it seems "Encryption at rest" gives Evernote the ability to have everything encrypted that they store on the Google servers, which is better than no encryption but it still doesn't give Evernote users the ability to have unique encryption protection with their own key. Someone would need to know the key(s) Evernote uses in order to access sensitive data, but a breach of Evernote security/keys would unlock all Evernote user data. So it's better (data is encrypted), but not really acceptable (because it's encrypted at the Evernote level not at the user level) - yet.
Looking further into Google Cloud Platform encryption at the link above, it does provide the ability for customer supplied keys, offered as a service that a customer like Evernote could use, without having to implement the backend support. So maybe the unannounced Evernote plan would be, once they complete the migration of their petabytes of data onto GCP, and get out from under the maintenance and support of their own servers, they can use what GCP offers to provide a much more robust encryption capability to Evernote users who need it? I can see how challenging it would be to build an encryption solution on their own proprietary back-end servers. That issue would go away with GCP.
Is this a reasonable theory?
It would be nice if Evernote would announce something so customers may decide to stop pulling sensitive data off Evernote - or at least be prepared to migrate back if the plan succeeds.