Rear wireless "surround" airplay speakers for iPad?

We use Bowers & Wilkens A7 airplay speaker as main/only speaker to play music rom an iPad (and TV audio, via Apple TV). Are there

wireless surround speakers that could work with this scenario? An A/V receiver would mix the sound and send it to multiple speakers (but I'm guessing this isn't the case with iPad)? If not, do you Apple will add this feature soon? Missing TV surround sound!