Microsoft has today confirmed that "no Mobile builds are coming" to Insiders who are still using Windows 10 Mobile and holding out for some kind of love from Microsoft. The company did originally state that more Mobile builds would be coming, but when asked if this was still happening, Jason Howard, senior program manager on the Windows Insider Team, said "Plans change. Such is the nature of things."
Whatever plans changed, it appears Microsoft is no longer committed to releasing new Insider builds for Windows 10 Mobile. Microsoft will continue to service Windows 10 Mobile with monthly security updates, but outside of that the platform will not be receiving any more love. As such, this means Windows 10 Mobile Insider Program has more or less come to an end, not with a bang but a whimper.
This shouldn't come as much of a surprise if you've been paying attention. Microsoft already confirmed that it was no longer focused on building new Windows 10 Mobile hardware or features, and with no new features means there's no need for any new builds. Windows 10 Mobile will forever remain at Redstone 2 with the feature2 branch as a result.
That doesn't mean UWP apps won't continue to receive updates however. For now at least, most UWP apps are still targeting Windows 10 Mobile, which means apps should continue to work just fine. This won't last forever, though, so be prepared for the eventual abandonment of Windows 10 Mobile altogether.