Hmmm, it does seem very likely that Sonos will soon introduce a soundbar to keep their collection of wireless speakers happy, having picked up the collective nod of approval from the FCC for their Playbar, where you can see the label right above. So far, FCC filings of the Playbar seem to indicate that this Sonos device will rely on Wi-Fi connectivity to stream music in a similar manner as that of other devices. Label location mockups of the device do indicate a rectangular object which should not be too different from your standard issue soundbar.
So far, Sonos has yet to step forward and make an official mention of the Playbar, but considering the circumstances and how it has already been announced by the folks over at the FCC, this does seem to indicate that the Sonos Playbar should not be too far away from being released. Hopefully, an official release date (accompanied by reasonable pricing, of course) will be made available to the masses sooner rather than later.