It's a little early to get nervous about not being prepared for the upcoming expansion, but it's never too early to start the preparations. If you start ahead of time, you'll never even need to worry about it coming down to crunchtime. Plus, if you finish getting ready ahead of time, you can take those last few weeks before Wrath nice and easy. Something I noticed a lot as we neared The Burning Crusade, everyone and their mother spent eight hours a day in battlegrounds that final month before the expansion, and by the time we could go through the Dark Portal most of them were burned out on playing WoW.
The absolute number one thing we can be sure you'll need in Wrath is gold. It doesn't matter what they do to your gear or your class, gold will be needed. Even if gold won't be worth as much as it is right now, you'll need it. You can be sure of that. Heck, even if you don't need gold for anything at all in Wrath by some miracle, it's cool, don't worry. 10,000g can buy you roughly 6,666,666 bottles of Moonglow when the Lunar Festival comes around. Think about that, man. Moonglow is awesome.
...Hm, I hope that math is right.