With leaks revealing the Lumia 630 and Lumia 930 the assumption was that both phones are getting ready to launch at the Microsoft BUILD conference, which starts tomorrow. But we've been seeing a lot of the Lumia 630 and virtually nothing from the 930.
A trusted tipster of NokiaPowerUser claims that the new high-end phone will indeed miss the BUILD conference. Other sources still claim that both phones will launch in April, but that doesn't necessarily mean at Microsoft's event (instead on April 19).
Windows Phone 8.1 is a certain participant of BUILD, even if the phones don't show up. Many details about it are still unofficial but the new OS version will be available for WP8 devices some time in early May, if rumors are to be believed.
You can see it in action in several leaked videos, running on the Lumia...