The Lumia 640 was only announced by Microsoft a few weeks ago, but many people are eagerly awaiting its release, slated for 'April'.
MetroPCS is evidently primed for the sale of the entry-level Lumia in 'mid to late May'. The date is slightly later than open market availability although it is not too far pushed back.
Cost of the device is looking to be $99 likely off-contract, although final pricing is not locked in 100% just yet. MetroPCS's version will support LTE although it is not clear if it will be dual SIM.
Full story from the WindowsCentral blog...