Swh,
That's all well and good, but most airlines do not use the humidity function because it has a negative corrosive effect on the metal tubes over time. So the 787 and eventually the A350 will be the only aircraft widely employing this benefit.
The bigger issue is passenger experience. I think it would be hard to make the case that the A330 offers anywhere close to the service potential of a 787. In addition to the aforementioned designs, the larger windows and ride have to be worth something.
I'm not saying the 787 is better (or worse) than an A350 will be, but it certainly kicks the pants off an A330. That said, the comments about purchase price are legitimate, and I'm sure Airbus will do what it has to do with the price to keep selling A330s... just as Boeing has with the 767.