Which ‘bar’? The Arc, or the Beam, or one of the older ones?

I would think you could unplug it…but at the same time, there’s a possibility that there is an issue with your network, so I’d want to reboot the router as well, before trying to update it again.

I recommend closing, then re-opening the controller.

For older models the recent update can take more time, though no “bars” are mentioned - could it be your surrounds or Sub taking longer?

https://support.sonos.com/en-in/article/release-notes-for-sonos-s2

Alerts: 

• With this update, we’ve adjusted how some of our older Sonos products are using their internal memory. Because of this change, updates for Play:1, Play:3, Boost, Connect, Connect:Amp, and Sub (Gen 1 and 2) will take longer to complete than before. The reset process for these products will also take more time to complete after this update.