This is an accepted solution.
Shopify Email is a very exciting feature, so I can fully understand the eagerness for it to launch platform-wide! At this time, we do not have an ETA to share outside of Shopify Email will be available early 2020. That said, you can request early access, which is approved on a store by store bases here. Once our teams have worked out the bugs, and have everything set to go, we'll be sure to announce the launch on our Announcements page.
Fingers crossed it won't be much longer!
Shopify Email is live now. I tried and made a post to share reviews and feedbacks. You can join it it to discuss the app: