This has been requested many times and we don't know what technical barriers there may or may not be.
What I do know is that the side-firing speakers on the Arc, bounced of the walls of my TV room, often give the Impression of sound coming from well outside the Arc itself.
There must be some compromise here, I know, but I'm happy with it.
I am not saying it's an unreasonable request though.
The Arc is a soundbar, that is designed to be FL-Center-FR. The design of the speaker must be geared towards this function. It is not a center speaker.
Just because the speakers in your new TV are wider apart does not make them better - it could even mean they're worse. "Just add some speakers” is not the way to design a good surround system, in which every speaker serves it's purpose.