The FCC presentations presented by Sonos in March suggest that the company is working on a new loudspeaker, possibly a continuation of the Playbar. The presentations, which were discovered by Variety reference model number S14. According to reports, the device will incorporate an HDMI port, which would be new to Playbar. (Previously it was based on an optical input port). The presentation of labels, which can be seen below, represents a microphone. This probably means that the mysterious speaker will be sent with support for Amazon's Alexa voice assistant, just like last year's Sonos One.
This is the presentation of the label; it looks like the Sonos One device interface:
Although most of the publications, including the German website iFun that apparently found a graphic representing the device, speculated that it might being an update of the Playbar, the presentation of labels represents a larger square device, which means that it could be a totally new loudspeaker or a Playbase update, although it was only launched last year, so it would be a quick change for a new model.