The WebUSB api has always been on the roadmap, but it got deprioritized for 1.0. It takes a long time to finish all these pieces, so some patience will be needed. :-)
Would it allow me to connect a USB keyboard (for example) or a USB mouse to my phone? How about a USB webcam that requires an additional linux driver to be installed? How could that be installed easily by the user? How about connecting a printer via USB? Will I be able to print from my HTML5 app? If not, what will it support? I'd also like to be able to find devices and printers via wifi and print, scan, etc. Will I be able to do that?
The ultimate goal is if somebody wants to do something, then it should be possible.