This whole conversation has started the lore loving community of WoW buzzing, as you can see in part from the Scrolls of Lore thread. There's quite a few theories on what this conversation could herald, some more outlandish than others, but most of them pretty fun to mull over.
First, there's the idea that this could herald some sort of change for Tauren Druids. While Blizzard mostly homogenizes classes even between factions, some are wondering if this is some change for the Druid class. Maybe Taurens will find their "own path" of Druidism based on the sun, the other eye of the Earthmother and the "balance" for the moon. It would be mostly cosmetic, replacing Moonfire with Sunfire and the like, but it might lead to a deeper understanding of Tauren lore and world lore in general as Tauren return to the "original form" of Druidism.
Of course, some people are a bit uncomfortable with the idea of the Tauren truly being the first Druids. In the past, blue posters have suggested Tauren mythology on the subject might be off, and that Malfurion, as established in other lore, truly was the first Druid. Retconning one of the great accomplishments of Night Elven culture does seem a bit unfair to them, to be fair, but retcons are a fact of life with Warcraft mythology.
There's also some more radical ideas about what this could mean for classes. Some people wonder if the sun, called An'she by the Tauren, could actually be an embodiment of the Light, and by discovering it, we could see Aponi become the first Tauren Paladin, perhaps triggering a wider, more permissive class spread for all races. Others wonder if the Sun, being a primary symbol of the Blood Elves, could lead to the Blood Elf Druids so many have wanted since that boss in The Botanica.
Of course, at the same time, people point out that the Light is already the balance to Shadow, so making it the sun and assigning it to balance the moon might be a bit much, especially since Druidic magic generally seems more primal and chaotic than holy magic.
This could also, some say, point to a new expansion and a new class altogether. This conversation, when people are already looking forward to the next step after Arthas dies, could be pointing to a Druid-specific expansion, such as the Emerald Dream, where Tahu could become the first Druid of the Sun, the new hero class, or at least the major representative of the Tauren in the dream.
I'm still thinking the Maelstrom is our most likely candidate for the next expansion, but then again, the Emerald Dream could always be a set of zones or a dual-focus of the lore in the Maelstrom expansion, especially if they decide to connect the Nightmare to, say, the Naga looking to get revenge on the Night Elves for their defeat during the War of the Ancients. But even then, I don't know that making a near-copy of an existing class is the way to implement a new class. It'll just make all the existing Druids feel a bit inferior for being the "old and busted" version of Druids. So I don't know that this is pointing to a new class, at least not one that is too Druid-like.
Of course, one of the simpler explanations, and one that might be my favorite, is that this simply foreshadows a move by the Druids to fight Arthas in patch 3.3. The Cenarion Circle has been sorely underrepresented in Wrath of the Lich King. Their biggest presence is in the D.E.H.T.A, a small group of fanatics who are primarily part of an elaborate inside joke about Hemet Nesingwary's animal killing quests more than anything serious. We've seen novel descriptions and comic book illustrations of Druids calling forth the true wrath of the wild to summon terrifying storms or cause trees and roots to grow instantly and overtake demons or choke cave entrances. The Cenarion Circle could take an active hand in the battle against Arthas in a similar way, and with Tahu sounding anxious to get to the front lines all of a sudden, we could see him out there at the head of a group of Druids, tearing down the walls of the Icecrown Citadel with the power of nature.
Whatever the true meaning of this conversation, and no matter what it might foreshadow, it's definitely a lot of fun to speculate, and seems to point to some pretty juicy happenings down the line, no matter what their nature. With any luck, maybe we'll see the quest line for these 2 character extend, or maybe even see a Night Elf/Alliance equivalent conversation that will provide more insight from another angle. If nothing else, I have a very good feeling we'll see more from Aponi and Tahu in patch 3.3.
Patch 3.2 will bring about a new 5, 10, and 25 man instance to WoW, and usher in a new 40-man battleground called the Isle of Conquest. WoW.com will have you covered every step of the way, from extensive PTR coverage through the official live release. Check out WoW.com's Guide to Patch 3.2 for all the latest!