I dont know if its possible or not but my staff and I are planning our big update around the release of 2.2 final and we have made changes to the TOS. So is it possible that once upgraded all members are forced to re-login and once they do they have to agree to the updated TOS?

maybe some mod can do this ?
Or mass revalidate or something ??

Surely a simple way to do this would be to announce sitewide that continuing use of the forums is subject to the new tos.

You put in your TOS the same thing many other sites put in their TOS that you reserve the right to change your TOS as often as you want blah blah balh.