I think banners might come back in convertibility when they stop acting like banners. Flashing text attracts they eye, but we are all blind to it. When a banner looks more like one of the pictures on the site, it usually gets my attention.
For example I visit a surfing site that has a lot of pictures of people surfing and I will usually end up reading a banner that has a picture of someone surfing and then a small amount of text.
Amazon has done a really good job about this as their ads are not banners, but mini stores. They don’t try to sell you on a concept, they try to sell you the product directly.
I think as we transition from looking at banners as ads to looking at them as rented real estate that you use to start your conversion funnel, we will have much better return rates.