According to a second leaked internal memo, T-Mobile US is set to kick off the Windows Phone Refresh (aka "Tango") rollout tomorrow, on June 27th. We previously received word from sources that June 20th was the destined date, but it seems as though the upgrade has been delayed slightly.
The Nokia Lumia 710 is the Windows Phone that will benefit from the update that will be installed via Zune (or the Mac Connector). Internet sharing capability, disappearing keyboard fix, as well as a number of other improvements, are bundled with introduced features which will please those who have been waiting patiently.
Be sure to keep a watchful eye on the lookout for any update notifications.
Thanks, Jacinta, for the tip!