1. Harry Potter --hah, you knew I'd go there, didn't you? Y'all are so smart. ;) I know we had seven glorious books, but I want more!! I want prequels about James & Sirius & Remus (not that rat, Peter, though). I want Hagrid's story and Dumbledore's and McGonaggal's. I want to know all about the children, James & Lily & Scorpius & Teddy. (The James Potter fanfic series by G Norman Lippert helps a lot with this last bit! The first was really fantastic.) I just want to be totally overwhelmed with the wizarding world by JK Rowling.
I want this next generation photo by Mox-ie to be real! :)
2. My Name is Memory by Ann Brashares --when I won a copy of this in 2010, I enjoyed it immensely but was super mad at the huge cliffhanger...until I found out she was going to turn the story into a trilogy. I anxiously awaited the next book, wanting to know what happened to the characters...and 3 years later, I am still waiting and it doesn't look like it is going to happen. I think that's even worse than just a standalone book with a cliffhanger.
3. Kiss & Make Up by Katie Anderson --not that this was the best book or anything, but I think it would make a fun series. Trying not to spoil anything, but the ending sets it up so that could happen at some point.
4. Friends With Boys by Faith Erin Hicks --a great YA graphic novel that is just begging for a sequel. So many things were left unexplained!
5. Delirium by Lauren Oliver --because the real ending blew chunks. :(
6. The Night Circus by Erin Morgenstern --I'd love to see the next generation of circus performers and magicians. Kind of like Harry Potter, I am just being selfish and wanting to see more of this world!
And...that's all I've got. Harder than I realized! Most authors know exactly when to finish their stories and have that perfect balance of wanting a little bit more but being satisfied where it ended. So what's on your list? Any that I mentioned?