Just have some patience, unless WoW stops having future expansions, the trend described below will continue.

Yes, Blizzard's revenue model is monthly subscriptions, but what they're really selling is player progression.

There's an obvious hardcore/casual dichotomy in Blizzard's customers, and the strategy for satisfying both is to introduce newer "tougher" content to usurp the old high-end stuff that's adjusted to become accessible to more players. These "adjustments" can include nerfing the encounters themselves, or providing easier access to better gear, changing PC spells to be more powerful, etc. Think of it as Blizzard's longterm subsidization of player progression between expansions.

It's ironic that Blizzard should call the expansion gear resets "leveling the playing field" when this is in fact the time when hardcore players truly pull away and distinguish themselves from the casuals (looking at it as a % gain in point allocation per gear tier). Once Wrath's first major content patch hits, purples will become easier and easier to get.

If you have no idea what I'm talking about, it's alright.
Just rest assured that Blizzard will eventually grant you purple epixx and ever increasing powers, even if they have to buff it into you.

So if you truly want to challenge yourself, you really only have about a six-month window in which to smash your head against new content in its most difficult form, before it gets nerfed and you get buffed.