Keeping the online manual up to date is obviously a priority, but I think that simply forking it and keeping older version of the manual online + assigning a "major release" to each of the versions would help avoid confusion and allow users with an older web2py to still access a manual that fits their version of web2py.
I usually tend to avoid making any software changes to my live server/ sites (which are not 100% necessary), assuming I'm not the exception - there are bound to be sites running older versions of web2py out there.
