I've been pondering this for awhile and I'd like to hear your guys' thoughts about it.
I started playing in vanilla, when there was nowhere near the amount of options that we have today. I'm going to use battlegrounds as an example. We had a whopping total of three. With each expansion we got a few new ones. Here's a list of all forms of "objective-based" PvP, grouped by the expansion they were first introduced in.
Classic
Warsong Gulch (BG)
Arathi Basin (BG)
Alterac Valley (BG)
The Burning Crusade
Eye of the Storm (BG)
Ring of Trials (Arena)
Circle of Blood (Arena)
Ruins of Lordaeron (Arena)
Halaa (World PvP)
Wrath of the Lich King
Strand of the Ancients (BG)
Isle of Conquest (BG)
Dalaran Arena (Arena)
Ring of Valor (Arena)
Wintergrasp (World PvP)
Cataclysm
Twin Peaks (BG)
Battle for Gilneas (BG)
Tol'Barad (World PvP)
Rated Battlegrounds introduced
Mists of Pandaria
Deepwind Gorge (BG)
Silvershard Mines (BG)
Temple of Kotmogu (BG)
Tol'vir Arena (Arena)
Tiger's Peak (Arena)
While Halaa isn't something you queue for like WG/TB, I threw it in there anyway because it was in a central location and was the "precursor" to WG, if you will. I realize I omitted a lot of smaller PvP areas such as the towers in Auchindoun and the areas in Krasarang Wilds. Adding up the list, we have 11 battlegrounds, 7 arena maps, and 3 world PvP zones. We know Ashran is the new WPVP zone in WoD, and we also know there will be at least a couple of new battlegrounds, although we don't know what they are or exactly how many yet.
Now let's look at classes. In the interest of saving space and avoiding redundancy of common knowledge, I won't list them all out by expansion, but we have 11 classes, 9 of which existed at launch, 1 that came in WotLK and 1 that came in MoP. Looking at races, we have 13; 8 at launch, 2 with TBC, 2 with Cataclysm, and 1 with MoP.
Where am I going with all of this? The issue at hand, or at least in my mind, is balance. The community is always asking for more. More content, more loot, more mounts, so on and so forth. It seems like every few days, a new thread pops up about the next hero class or the next races to be introduced. My question is, is "more" always a good thing? When does "more" become "too much"? Some things, if we are given more of, do not affect gameplay as much. New mounts, for example, would be welcomed by just about everyone, and since mounts are purely cosmetic, no real problems arise from introducing new mounts. However, things such as classes, races, and battlegrounds have more profound effects on our game.
I am of the opinion that for those things, more is not always better, no matter how much people may beg and scream for being able to play as an Ogre Tinker or an Ethereal Demon Hunter. With the 11 classes we currently have, the devs already have a difficult enough time trying to balance them. The same goes for races, which is why racials are being redone for WoD. Wouldn't adding more further complicate things? And as for battlegrounds, there are a few which are currently very one-sided favoring one faction or the other when it comes to W:L ratio; and this is not just anecdotal, there were statistics that came out not too long ago showing just how skewed some of the win percentages are. There are even some battlegrounds that practically nobody wants to play due to balance issues and/or poor design (IoC, I'm looking at you).
Wouldn't adding more be detrimental to the health of the game as a whole? If there are things that are currently broken, why are new things being created and introduced when the time could be spent fixing some of the old problems? What happens when we end up at expansion #8 with 20 different battlegrounds, and only a quarter of them are actually enjoyable, while the rest are imbalanced, broken, or simply outdated? Or 16 different races, but only 4-5 that are played by the majority of the population due to OP racials? There's a reason why most of the top PvPers play human, and its not because of how they look.
Another way to look at it is like this: if WoD came out (or whatever expansion after that) with zero new classes, zero new races, and zero new battlegrounds, would you still play the game? What if their reasoning for not having any of those things is that "we have enough" and that they want to balance what we currently have? Would you view that as Blizzard being "lazy" or doing a "half-assed" job?
In a time and age when the playerbase is always wanting more, I can't help but wonder if I'm the only one who is content with that which we already have. I know the guys in the Tinker thread are probably going to disagree. Just wanted to hear what you guys think about this.
I'm going to leave (PvE) content out of this discussion, because more content is almost always a good thing. PvE content is the medium through which the story is told and is a means for our character to progress, be it through leveling up or obtaining new gear. Because they are scripted encounters and are done linearly, they don't face the same problems with balancing that new classes or new BGs do. Once a new tier of raiding comes out, the focus shifts almost entirely to that tier; nerfs are often applied to previous tiers and new, easily-obtainable gear is introduced to help players "catch up" to the new tier. This is a different philosophy than PvP, in which all battlegrounds can still be considered "current" and "relevant", no matter when they were introduced.