According to the Bitmain website, the $800 Antminer E3 unit will ship sometime in July. The company will allegedly be limiting orders to one unit per customer and will restrict shipping to China and Taiwan.
With the current specs fo the Bitmain Antminer E3, CryptoCompare estimates roughly $90/month profit (though actual numbers might be much different).
All that being said, it remains to be seen whether the ethereum network will impart measures to prevent the use of the forthcoming ASIC via protocol changes. Last week, a dev released an ethereum improvement plan which proposes a network hard fork to prevent the use of ASICs.
This would esentially render the unit useless, at least for mining ethereum, so buyers should buy with caution.