Bornakk has pretty much laid down the law. Eight piece armor sets are dead as we know them. Despite Claymore from Medivh's call to bring them back, Blizzard is happy with the way the five piece tier sets are working out, and that's the way they're planning to keep it.
Kind of a shame, because as Claymore says, seeing someone with a full eight piece set was pretty epic. It took a lot to pick up every since piece, and some of the eight piece bonuses were pretty cool for their time. But just like the 40 man raids, there were lots of problems with eight piece sets as well. I never completed mine, just because my guild had moved on from where the gear was dropping before I was able to pick all the pieces up. And five piece sets give a lot more options as to customization-- with the extra, non-set pieces, players can choose to focus on a certain stat over others, which couldn't be done with the full eight piece sets.
So in general, it's a good move-- bigger is not always better. Nostalgics may long for the days of Bloodfang and Giantstalker, but five piece armor sets are here to stay.