I think Firefox is trying to adopt the Chrome model, which is that version numbers are for the developers only. End users shouldn't need to know which version they're running.
no more of this "i'm going to stick with version 3.6 for now because i prefer that" nonsense. there is only up-to-date and outdated. yeah, it's a subtle and mostly psychological difference, but it is a difference.
and then they respond with 1001 reasons why they can't update (security restrictions, corporate policies, etc).
There has to be a line drawn - where do you draw it? If 5.0.1 came out yesterday, do you not support someone who is running 4.8 which came out 3 weeks ago?
they respond with 1001 reasons why they can't update, you come back with "well that's too bad". the only way to change people's attitudes toward browser updates is to not tolerate outdated software. if we keep accommodating crappy IT departments, things will never change.
