Two years later, we have plenty of information on how the dual spec system works. Its initial price tag of 1,000 gold kept it limited only to the most serious of players, but even that high cost couldn't keep the more casual set away. The pricetag has since been slashed all the way down to a mere 10 gold, making it something that everyone can, should, and will train. Dual spec has become so popular that Cataclysm's new stat system seems as if it was built around it. You can now be a successful shadow priest and healing priest in the same gear; a feral DPS druid can change into an able feral tank with very few gearing changes.
Dual spec's been such a terrific and natural fit that it's hard to imagine the game without having it. To that extent, it's been a smashing success. And so, if dual spec has worked so well, why not consider triple spec? For paladins and druids especially -- both of whom can heal, DPS, and tank -- it'd be a godsend. Triple spec would lead even more people to create a PvP spec, an aspect of the game that Blizzard wants more of us to experience.
Unfortunately, triple specs aren't on the horizon, or so said Community Manager (and blue poster) Bashiok on the official Blizzard forums today: