I think this is just live version of song which in studio is performed by Jon.
Many DJ has live musicans which singing his hits live.
I can easealy see that Avicii wrote this demo with that guy (who sing on this preview) and tried to find famous artist which sound similar and has more recognaizable voice.

I think Jon's voice will fit well on that one and I think that if they'll realise this on single it will be another Avicii huge hit.