When you create through
virtualenv python3.0
It creates a symlink in the virtual env folder bin directory :
lrwxr-xr-x 1 --- --- 6 Aug 23 13:28 python2.6 -> python
So you can not do just pip install to upgrade python.
On mac osx, you can have multiple versions of python installed. In your case , install Python 3.0 and then use that version to call the virtualenv.
Python is installed in /usr/bin
-rwxr-xr-x 2 root heel 86000 Feb 11 2010 python
-rwxr-xr-x 5 root heel 925 Feb 11 2010 python-config
lrwxr-xr-x 1 root heel 75 Aug 23 10:01 python2.5 -> ../../System/Library/Frameworks/Python.framework/Versions/2.5/bin/python2.5
lrwxr-xr-x 1 root heel 82 Aug 23 10:01 python2.5-config -> ../../System/Library/Frameworks/Python.framework/Versions/2.5/bin/python2.5-config
lrwxr-xr-x 1 root heel 75 Aug 23 10:01 python2.6 -> ../../System/Library/Frameworks/Python.framework/Versions/2.6/bin/python2.6
lrwxr-xr-x 1 root heel 82 Aug 23 10:01 python2.6-config -> ../../System/Library/Frameworks/Python.framework/Versions/2.6/bin/python
/usr/bin/python3.0 virtualenv yourenv.
This env will have a symlink for python 3.0