From what I understand - if the hash rate is exactly the same in 2000 blocks time, then the difficulty remains the same. If the hash rate goes up by 5%, then the difficulty goes up by 5% as well... so it would be 8,056,650. In the same way it could go down.
If the hashing rate goes up for the next 1000 blocks and then falls back down to the same rate as today, then the difficulty stay the same. It's dependant on the hashing rate at the exact time we reach then next 2000 or so blocks.
I *think* that's right. Someone please correct me if I'm wrong....
yes, you're right. Although it's 2016 blocks. And luck also figures in the equation. Only "how much time passed since last change" affects new difficulty change.