Dona Sarkar and the Windows Insider dev team dropped Build 16921 for PC today but stated that no mobile build would be released.
Resume from PC to phone using Cortana is listed as a feature at the Windows Insider blog along with the following:
General changes, improvements, and fixes for PC
• We fixed an issue where sometimes after an upgrade Windows Update’s update history would be missing a listing for the feature update you’d just done.
• We fixed an issue where scrolling with touch or precision touchpads wasn’t working with the F12 Developer Tools.
• We fixed an issue where pin reset above lock (“I forgot my PIN”) would only work the first time the password was reset.
• We fixed an issue where Microsoft Edge would crash if you added a Favorite to a Favorites folder and then immediately sorted that folder by name.
• We fixed an issue with the indexer from recent flights that could result in Outlook 2016 search failing to index the body of messages.
• We fixed a recent issue resulting in the Skype UWP app not being launched if it was minimized when you clicked an incoming call notification.
See more about the latest build here.
* On a surprise note my Lumia 950xl is currently downloading Build 15252.0 (feature2). Not sure if I missed a build along the way or this is a mistake by Microsoft. Will post back if anything out of the ordinary shows up.