The average player is probably about where I am – heading into Ulduar weekly, doing some Heroics for sweet T8 loot, and starting to tidy up most of the solo content in the expansion. It's increasingly looking like I'll be "done" with Wrath by the time Cataclysm hits, with maybe enough time to get a second toon to 80.
And that's why I don't subscribe to the "WoW is in decline" feeling you see expressed in the Blogosphere whenever another big name blogger quits. Almost by definition, if you're a big name WoW blogger, you're not an average player. And Blizzard is, more than ever, tailoring the game to people who are average. That means that the above average players are going to burn through that content quickly – but then, that's what the hard modes and weird-ass achievements are there for. For a small group, for the one who are dropping late-instance bosses a few weeks after new raid content is added, that may not be enough. But I have a feeling that they're a small, small part of the player base.
I'm actually enjoying the game more than I have ever done right now. Dailies in the morning, heroics with my guildies in the evening, raiding once a week most weeks, and some work on Loremaster when I have time left over. It's great fun, it's the right balance of time (my other half isn't grumpy about my playing any more), and I genuinely feel like I'm making progress each week, be that bosses down, new gear, reps done or cute little pets acquired.
I have a feeling that Blizz have WoW in a really sweet spot right now, one that will keep a very large number of players happy for a very long time to come. If they can up the pace of the expansions a little – getting Cataclysm out by the spring of next year and the next one by the summer of 2011, I think WoW will cruise into it's tenth anniversary with big numbers still playing.
Right now, I certainly hope so.