Eh. I'm not buying an Inception sequel. This definitely feels like it's another secret original idea. I wouldn't be against a sequel or spin-off, but I just feel like Nolan wouldn't be spending these last few years working on a sequel. Doesn't feel like a move he would make who knows. My money is on an original idea. Although exploring the Inception universe sounds interesting, just doubt it.
If it does end up being something organically grown from the concepts of Inception, I think a ten year gap between the films leaves a lot of good breathing room to differentiate both of them. I’m sure he’s reflected on the world and explore other elements that don’t relate to Dom Cobb’s storyline.
That being said, I’d rather to be blind sided by a wholly new and unexpected world.