As for what Sonos will leave out to hit this lower price point, the Fury won't be able to output Dolby Atmos content like the Beam and Arc, and it may not even have an HDMI port; you'd hook it up to your TV with an optical audio cable. As such, it has fewer speaker drivers in it than other Sonos soundbars. It will be able to be part of a 5.1 surround sound setup using other compatible Sonos speakers — we presume that you can use speakers like the Sonos One as rear surrounds like you can with other Sonos soundbars.
One potentially intriguing feature is that Sonos will let the Fury work as rear surround speakers for a bigger soundbar like the Arc. As such, Sonos is apparently making vertical mounting stands for the Fury so that it can be used for Dolby Atmos content.
There are plenty of budget soundbar options on the market from the likes of Vizio and Roku, while Sonos recently raised the prices on nearly all of its products. The original Beam sold for $399, but the new one costs $50 more, making for an even bigger gap between Sonos home theater options and those from more affordable competitors. As such, this is a pretty logical part of the market for Sonos to get into, and it's not hard to imagine a $250 soundbar being a good product to get people into the company's ecosystem.
Sonos declined to comment on today's leak.