no, for several reasons
i) you assume guild size based on players actively pvping, which is silly, lunchbox for example really doesn't have a huge amount of pvpers that are very active in 50 pvp, but we have three 8man hm tfb/nim ec raid groups going, which leads to the next problems
ii) almost all the mentioned guilds will have a set way to run and manage their guild, what you are asking would be the same as going
"hey canada usa and mexico, you're all in the general area, merge your governments and split the power, position and national funding together"
it is a bad idea.
iii) the last problem i will mention is the fact that many guilds have invested a lot of time and money into guild websites, vents/t.s/mumble etc etc, which do we use? who pays for it? who gets control of it? all of there things are serious issues that would prevent a big server merge.
in the long run if it would work, i would absolutely love the idea, but there are just too many issues, and as somebody said before, not enough incentives for guilds other then really small ones to merge.