Well, I have plenty of patterned paper and still use it in scrapbooking. I do use some patterned paper on cards, usually as a matt. I like using the smaller papers on cards because they have the designs scaled down for card size. Some of the 12 x 12 patterned paper have such big sized patterns that they do not work all that well for cards. I haven't bought patterned paper for quite a while except for the occasional 6 x 6 sized tablet.
I have also noticed the lack of patterned paper in cards lately. I think it is because of the cost for one thing, paper prices have gone up; but also because all the "new" patterned paper look alike. The new lines all look like something I already have so I have passed on purchasing anymore patterned paper. If I don't like what I have I coat it with gesso and add the color I like or just use it with a light coat of gesso to tone down the colors already present in the paper. Right now there are so many kinds of media that make good backgrounds that one doesn't need patterned paper to make an interesting card. I think distress ink has taken the place of a lot of the colored card stock for backgrounds on cards. I see many card artists using distress ink to color the backgrounds to match their main focus. This makes sense to me because no matter how many colors or patterns of paper you have it always seems like nothing matches "just" right to the ink and colors so distressing the background to match is an easy alternative.
If you buy one good set (or in my case many) of watercolors you can have any color background you might want. I see watercolor also taking over the background stage. If you take the same colors you are using for the main focus and watercolor a background with a lighter variation of those colors it is win/win.
Then there is water soluble inks, crayons, neocolor IIs, prima pastels, colorblocks, inktense blocks, and many more medias that work so well on backgrounds that the need for patterned paper is just not there anymore.
I would assume that this trend towards different media on backgrounds instead of patterned or colored card stock is circular and it will once again come around to patterned paper as soon as everybody offloads most of their patterned and colored card stock......LOL. The paper crafting industry has to reinvent itself with different media to keep selling stuff to us crafters. If you already have a roomful of patterned and colored card stock then they need to sell us media to make that patterned and colored card stock obsolete. It's all in the marketing. But as soon as enough people have moved on from patterned and colored card stock it will come back.
Once everyone has tried all the different media and a lot of those people decide that using that media is just not for them, but they got rid of most of the paper because they weren't using it, then some wonderful new line of paper will come out (that is if there are any paper manufacturers left by then). If you look at the crafts that have come and gone in the last 20 years you can also see some of those things coming back again for the second time.
My worry is that there doesn't seem to be the younger generation coming into the paper crafting, they are not printing pictures but rather using facebook and other social media as their scrapbooks. They are not sending cards, they are eviting, ethanking, and eRSVPing. They are having online parties instead of "real" parties. The newer people coming into the paper crafting arena are more interested in the "haul", the wonderful craftrooms, and the mixed media or planner areas in my opinion. Which is fine but I am afraid that we are also going to see more paper companies going out of business.