According to “industry sources” claimed by Digitimes, the latest rumor concerning what will be revealed at the June 20th Developer Summit is that a build of Windows Phone 8 will be released to manufacturers. This build will be far from RTM, as June is very early for the planned release of Windows Phone 8 code named Apollo.
This release of Windows Phone 8 to manufacturers, if it does happen, will simply allow select manufacturers to begin working with the operating system through a beta of sorts. Expected manufacturing partners to receive this early build of Windows Phone 8 will most likely be Nokia, Samsung, HP, Dell, Acer, ASUS, and Lenovo.
Sources also call out the fact that manufacturers will be joining the Windows Phone market, who in fact do not normally produce mobile devices. This again is a rumor, so it is not confirmed if any new and unique manufacturers will come to Windows Phone.
Finally, manufacturers are expected to release new devices during the Windows Phone Developer Summit. Microsoft usually provides a list of which manufacturers will have devices launched during events, so the list should be coming soon.