Windows 10 Mobile Build 10586.164 may be next cumulative update.
According to some leak build 10586.164 may be the next update for windows 10 mobile.. as the Windows 10 Mobile Build 10568.122 is already in slow or released preview ring which is very stable and smooth.. almost smooth as windows 8.1. and this new build will also bring some bug fixes and improvement which take the windows 10 mobile close to official release.