I'm encountering this problem myself under Sierra (using beta release 16D30a) - I've already gone a couple of rounds with Apple for other issues with the 2016 Retina MacBook (I encountered the
flickering screen connected by USB-C to HDMI problem last year) and had success. The question I have is - is there some specific issue that the DisplayLink driver developers have detected that I can report to Apple? Or do I just say, "when I have a USB-connected external monitor hooked up the internal display sometimes doesn't wake up?"
I should note that for me, at least, this problem is intermittent - sometimes it happens, sometimes it doesn't. I've been able to recover by simply closing, then re-opening the MacBook.