I've heard a lot of statistics from various sources stating that the rogue population has been dwindling since Wrath of the Lich King was released. Whether our decline is due to former assassins deciding to try out the new death knights, or rogues simply moving on to greener pastures, we may never know. I do, however, know that there's also a lot of newly minted rogues, working their way up through the levels and lowbie zones. And if there's not, there should be!
There's a lot of fights that are absolutely amazing for rogues, with Yogg-Saron hard mode (no keeper) and Anub'Arak hard mode being two of the most prevalent and important encounters currently in the game. I have seen guilds beg their inactivate rogues to resubscribe with promises of gold, crafted epics, and endless heroic runs to gear them out. I know of a rogue on my server who went from newly 80 to better geared than myself in about a month with a ton of help from his guild and friends. Many of the world's top guilds are looking for solid rogues to fill the shoes of those who have given up the mantle of shadows in the past year.
We've also got a lot of new rerolls who are working on getting a new class to 80 for Cataclysm's upcoming release. I have been working on a guide for those rogues who are new to the class (and possibly the game) who are looking for tips and tricks for getting the most out of their roguish experience. I would also ask that any veterans or novice rogues alike add their own tips in the comments, if you've got a personal anecdote or bit of info that made your time leveling easier.