Hacks at Ars Technica have found evidence that Vole is still working on such a phone in the latest Windows 10 Insider Preview.
Apparently the preview has a set of new APIs for mobile phones and while Vole has supported cell modems since Windows 8, it was always restricted to supporting data connections.
This means that dialing numbers and placing calls needed Windows Phone or Windows 10 Mobile. This has made the full Windows 10 unsuitable for a phone.
However, Windows 10 build 17650 -- a preview of Redstone 5, the next Windows update after the delayed April update -- includes some telephony APIs. The new APIs cover support for a range of typical phone features: dialing numbers and contacts, blocking withheld numbers, support for Bluetooth headsets and spearphone mode, and so on and so forth. There also looks to be some kind of video-calling support, suggesting support for 3G or LTE video calling.
The telephony APIs don't appear to be new: they match the telephony APIs already found in Windows 10 Mobile, so their presence in a build of desktop Windows might be nothing more than a mistake or the result of some kind of consolidation effort to reduce variance between Windows versions.