Actually, there is an upgrade going on: the GPU-> ASIC transition.
The network hash rate is increasing so fast that the next difficulty adjustment is going to be huge.
<phillipsjk> ;;diffchange
<gribble> Estimated percent change in difficulty this period | 23.33054 % based on data since last change | 39.67409 % based on data for last three days
So blocks are coming about 23% faster now. (or 40% faster, depending how you count.)
The increase has got to level out eventually, but there is supposed to be a lot of hardware arriving in the fall.