Keep in mind that (1) these are based on a healthy mix of data and anecdotal evidence, and (2) these are my thoughts on what seems to be selling now, not what will necessarily be popular in a year (the earliest your book would come out, assuming it's acquired in short order).
Graphic novels. It's likely these are seeing a bump because summer is superhero movie season, but it's pretty clear that this category is up from earlier this year. And (according to BookScan) it's not just properties with movies out/forthcoming, such as Thor or Green Lantern, so if you happen to be a graphic novel type of guy or gal, this is good news for you.
YA apocalyptic fiction. This (to my mind, anyway) was probably touched off by Suzanne Collins' The Hunger Games in the same way vampire mania was touched off by Stephenie Meyer's Twilight series, but I feel like I'm seeing an awful lot of end-of-the-world scenarios (Harold Camping's failed Rapture prediction and the New Age folks' Mayan 2012 nonsense notwithstanding).
Weird diet books. I've seen everything from "only eat raw foods and if you eat a cooked vegetable you will die" to "feel free to eat your weight in bacon." Some of this is probably seasonal—while a ton of diet books come out in January, I figure there's always a beach season bump—but I feel like I've been getting an earful about Paleolithic diets, raw food diets, Mediterranean diets, and no- or low-carb diets for months.
Thrillers/horror novels. While I still firmly believe the mass market paperback is on its way out, sales appear to be holding steady in this format for thrillers and horror novels (not so much straight mysteries, for some reason). Again, it's beach season, and I imagine anyone without a Kindle is buying a stack of inexpensive paperbacks for the beach or pool.
Romance. A perennial favorite, romance is probably doing well for the same reasons as the aforementioned thrillers—it's generally inexpensive and great for beach or poolside reading. Romance readers also tend to buy repeatedly and generally buy more books per purchase than other readers, so the effect may be amplified by those kinds of consumer habits.
That's all I've got for today, cats & kittens. What books have you been hearing about/reading about/seeing everywhere lately?