USB 3 ups the
max current to 0.9A, so you might be able to get nearly
5W, which is still, as you say, not really going to keep coffee warm.
I think you guys are missing all the real breakthroughs in USB
technology,
<SNIP!>
Some synopses might help, for those of us who can't afford the time to
sit through three Youtube videos.
Peace... Sridhar