On a question of just performance, how does Python 3 compare to Python 2.x?
Unless there are plans for a new VM of some kind (and I haven't heard of any such plans), there is all the reason to believe that in the long run the performance of Py3K will, at least asymptotically, equal that of 2.5
It may take a few months, but will eventually happen, as nothing in the new features of Py3k is inherently less performant. 
To conclude, I don't think there's place to worry about it. Neither to hope for a major improvement of some kind.
Performance: Python 3.x vs Python 2.x