S250 has posted over at TFW2005 in this thread images of what appears to be a show-accurate Masterpiece Starscream, titling his thread "US version MP Starscream."  The toy show in which the figure appeared is unspecified, but the debate about its authenticity is raging on in our forums here .

As of now, it's best not to be too optimistic, but there are signs pointing in either direction.  Join the discussion and decide for yourself in the thread by xZAOx.

UPDATE: S250 has received confirmation from another source that this IS a Hasbro toy, possibly to be released in September.