As you may know, Canonical has been working a lot lately at the Ubuntu Touch OTA-6 Update, which is currently under the feature freeze.
According to Łukasz Zemczak, one of the Ubuntu developers, the OTA-6 update may be delayed, due to a PulseAudio issue. Despite the fact that the developers have already patched it, the software is not stable enough for massive usage.
As a reminder, Ubuntu Touch is a stable operating system, but it is not mature enough, compared to Android and iOS. For now, there are three Ubuntu Phones: Bq Aquaris E5 HD, Bq Aquaris E4.5, Meizu MX4, but the system is also officially supported on the LG Nexus 4 device.