There was a preview of Popmart in the Elevation Boston DVD. Then Gone from Popmart was in the Best Of 1990-2000 DVD. That's all you're going to get for now. It is highly doubtful if U2 will release Popmart. If they go through their back catalogue, they'll start with the earliest before finally moving to Popmart. So I'd expect Under A Blood Red Sky then Zoo TV Sydney then Best Of 1980-1990 to make the DVD rounds before Popmart.
Cheers,
J