Yeah.. I don't see that ever happening again. Alliance or Horde.
...This server has. When I was in PvD during Ulduar we reached 68 world rank 10m after clearing all hard modes, recruiting was a !@#$% but we still managed to go places. The Revelation ring a bell also? They did amazing before they died. We also had Cold on this server for a while. All these guilds were at least top 100 US at one point on this server, hell they were even top 50 US.
I too was in PvD for a short while. Remember what happened to them? Transfered off.
The Revelation also died/transfered off a reeeeaallly long time ago. In WotlK Eco tried bringing a lot of them back and he did, but alas, The Rev 2.0 died. Damage and Healing went strong from early Wrath to late Icecrown, though.
Same deal with Confirmed/Contempt, eventually died off (although Contempt appears to be making a come back this tier);
Cold was mediocre and also transfered off eventually.
In Cataclysm we had Workin as Intended, Sinfest, Cthullu and Pants Optional/Malice which I was also a part of. All of them either died or xfered off (or both).
Seeing a pattern here?
The Rev was the last great guild to actually make Gul'dan a home. PvD did as well to some extent but they weren't around as long.
When was the last time Gul'dan had a guild as good as nerdcraft or any of the above stay for longer than a couple of months?
edit: to address the bolded part, I'm obviously aware it has happened in the past. All I'm saying is people have learned their lesson.