Ah, the reasons I don't want a sequel are too numerous to count.
1. I don't think the gameplay can get much deeper without becoming too convoluted. (Which some argue it already is)
2. The current plot lines that haven't been resolved could easily be resolved with a big expansion.
3. For a sequel to be warranted, it should build on the game in almost every single way. (More often than not, this doesn't work out for sequels)
4. An expansion is warranted, when pieces of the game can be polished and improved, and utilized in further content.
With that being said, a sequel wouldn't surprise me. I would just rather an expansion and a new IP from these amazing devs. <3