It’s not to be released until July 13, but Wizkids has announced that Marvel HeroClix: Captain America has sold out at the manufacturer level.  From the Wizkids release:

The Marvel HeroClix: Captain America expansion will feature more than 60 figures in standard five-figure boosters.  Celebrating 70 years of comic book history, Captain America’s allies and enemies will be spotlighted prominently in this long awaited addition to the HeroClix universe.  Sub-themes in the set will include: the Serpent Society, S.H.I.E.L.D. Hydra, recent fan favorites the Secret Warriors and more! And making their bold debut in HeroClix, removable elements will enhance the action with exciting in-game effects and abilities!

Distributor Alliance had to stop taking pre-orders 13 weeks before the release of the series.  Wizkids is currently exploring additional avenues to create an additional print run to support in-store organized play.