Python 2.5 shouldn't be replaced by 2.6! It it correct that all programs coded for Python 2.5 will run with Python 2.6, but Python 2.6 is somewhat slower than Python 2.5 and thus you'll add more problems to the list of "TLE with Python"-problems. Many AC Python solutions would get TLE if rejudged. As Python 2.5 (especially in combination with psyco) is the fastest Python version ever, it should never be replaced!
Instead the second Python branch (actually with Python 3.1) should be updated to newer versions from time to time.