I don't think CPU mining hit limit. When more pools are available, more people may join mining. It's hard to estimate how much more mining power one can benefit from GPU, maybe less than 10, or maybe more than 100. The algorithm can be improved too, although we may need some serious mathematicians to take a look...
Block time seems to be roughly around or above 1 minute now.
Are all the botnets priming away? Or is that why the block times are so normal?
EDIT: nvm seems it was only for a few blocks.
It's not just for a few blocks. The difficulty is decreasing. Seems we are stable around 9.24, for now.
That would explain the difficulty decreasing by .001 over the last 3 hours.
Now that CPU mining has hit it's limit, what will GPU mining bring?
If you know something about Big Number calculation and the nature of GPUs, you know it's a lot harder for the GPU to do prime test than to do hashing.
GPUs don't like branching and memory access is also limited.