I'll find out soon enough. I ordered one today. (Got it for $30 on a Black Friday Deal)
I was able to find a workaround if I want to use my Bluetooth headphones with my 4670x. I paired the headphones with my LG TV, not the Roku itself. The downside to this is I need to use the LG remote control to dismiss the popup that comes on screen when I turn on the headphones. So it's not ideal to have to use 2 remotes to watch TV.