It's already being done.
You've got a 2.1 system. It's taking a 5.1 signal and "downconverting" it to 2.1 so it can play it.
Unless you're running a cable from the blu-ray player to the TV, and from there to the sound bar. In that case, the TV is most likely downconverting it to 2.0
If you want 5.1 through-and-through, you've got to go back to ground zero and start all over aain with a receiver, 5 speakers and a subwoofer. Then you can get 5.1 from your sources.
Anything you feed through your TV will be most likely be passed thru as 2.0, like it is now.