I think lightweight is there, but not what we call ultralight. The message is out that you don't have to take 50# for an overnighter and I think there are many who are in the low 20# range. There are hurdles with clothing, shelter, sleeping pads, cook systems, toys and gadgets.
Other than leaving the obvious junk at home, I think the difference between a 20# kit and a 12# one is how Spartan a setup you can handle. If I start adding to a SUL gear list it is over my head and under my butt :)