Gabriel Aul, the man whom you can trust with all the latest info and responses to your Windows 10 Desktop and Phones queries has teased the insiders and at the same time has confirmed that testing is going fine and it should be out soon.
We just reported a build of Windows 10 for Phones, 8.15.12492 from WPBench, with our sources later confirming about it being the latest build under internal testing. Gabriel Aul has tweeted from his device running Windows 10 for Phones (obviously).
@NicholasHayman Working as fast as we can. Coming along nicely. (Sent from Win10 on my phone