I'm a little worried we won't be able to time travel. I think we will, but I still worry. I don't especially plan on doing it, but it's nice to have the option. I also wish I knew more about the limits of terraforming before picking my map.
I keep wondering how designs are going to work. If New Leaf and HHD qr codes can be used, I'm assuming that means we have the same size canvas. I was sort of hoping for a bigger one so we could fit more detail. Previously, I had been concerned with custom designs looking pixelated and weird compared to the rest of the game's graphics, but it seems like they do some kind of automatic anti aliasing to make them smooth. So now I'm worried about how that could affect very small details in custom designs!!!
There are a couple things I really hope they improve, like more varied dialogue for villagers!
I think most of my concerns are personal. My life has changed so much since I played New Leaf and I have a harder time focusing on video games these days, especially for prolonged periods of time. I'm worried I'll play with it a lot for maybe a month and get bored, or that between school, work, and family obligations I won't have much free time to play at all.
Overall, I'm still very excited though! The hype definitely outweighs the trepidation, I cant wait for March 20th!!