I've just read that the real life F-35 AA-1 has been officially retired by Lockheed Martin after 91 test flights and 3 years of service. But instead of being placed in a museum, it will be the subject of live fire testing for battle damage assessment purposes.
AA-1 is(was) the first F-35 test aircraft built, and it is(was) roughly 5000 lbs overweight compared to the current CTOL test aircraft, named AF-1 which took flight for the first time in November 2009. And it is the only model that will be depicted in the Beta.
EDIT: Here is a link to a montage of the AA-1 test flights straight from the JSF website