We have received a tip from a trusted tipster that we will only see Lumia 630 at BUILD 2014. The tip says, Nokia may also launch some new apps at BUILD, but if the tipster has to believed there will be no Lumia 930 at BUILD. Though, as some of our other sources have confirmed Lumia 630 and Lumia 930 are coming in April, but they mentioned nothing for BUILD, so this looks better.
The tip further claims that the developer preview will be released on or around 8th of April. If you remember preview for developers app lets you update your device to latest OS version from Microsoft and if you have a app studio account it becomes a free update.
The third claim that the tip makes is about the public OTA release of Windows Phone 8.1 for existing devices. It seems Windows Phone 8.1 update will start rolling out to all Windows Phone 8 devices in early May.
If you want to read the most comprehensive Windows Phone 8.1 changelog on the web, click here.