I have to say that the changes that Rogues can expect aren't of the world-shaking variety, but many of them serve as excellent clean up improvements.
A number of these initial changes can be lumped in the "that's-great-probably-should-have-been-this-way-all-along" category. Even so, let's spend just a moment discussing them.
For a start, WotLK has removed the need for at least two kinds of reagents: lock picking tools and Flash Powder. I'm not sure Rogues were really suffering for the two bag slots or the on-going reagent cost for the powder, but I suppose that it's one less thing we have to think about when spamming box-opening skills in trade channel. Most Rogues I know use an automated poison mod Hemlock that will automate the purchasing and creation of poisons and Flash Powder so running out wasn't really an issue (or was it?).
Another small change is to Deadened Nerves in the Assassination tree, which will reduce all damage by 1/2/3/4/5%, which is a change from physical damage only. I see this as yet another talent clean-up since damage mitigation should not be based on style (e.g. casting damage vs. smacked-in-the-face-with-a-big-stick damage), and really, if I've sunk 30 points into a tree, that talent really should be a little more multi-faceted.
While we're still lumping the minor changes, both Kick and Gouge received a shiny polish. Gouge, an in-combat talent that incapacitates the target for up to 5.5 seconds (fully talented) and causes 105 damage has been buffed to require only a single talent point (down from a maximum of three) and will have its damage modified by attack power. I don't have the calculations yet on what the overall possible damage may be but I'd expect it to be consistent with other Attack Power modifying skills. Frankly, I'd be willing to move the Gouge change into the more substantial category of "I-can't-wait-for-this", but I'd have to see its use in PvP first. Kick, a highly desirable PvE and PvP skill, was adjusted to remove the damage component and reduce its talented portion by giving it just one level. I'm not really sure why kick ever had a damage element (I checked the tool-tip, and it's not "kick in the groin"), and you know it's not really a scale-tipper when you don't ever see any PvP videos regaling the "highest kick crit evah on cloth....over 9000!". I'd like Kick to have a shorter cool-down though, ten seconds can really be forever.
Changes with bite
Ok, we can now move on to the changes that I'm most happy about and would really like to see in action. Primarily, Rogues are constantly balancing Energy vs. Combo Point generation and talents that can add points based on passive skills are win in my book. Setup, which can generate a Combo Point on a dodge or resist (by you) has been buffed to 33/66/100% based on points allocated. This can be a really big improvement in PvP since dodge and resist stacking abilities; talents and gear is core to the class. With a high degree of dodge a rogue can have a 100% chance to add combo points, which improves the point to energy ratio since the combo gain was passive. Nice.
Premeditation, a talent in the Subtlety tree, can be activated while in Stealth to add two immediate combo points to a target, useable within ten seconds of application. This was buffed to twenty seconds, a really nice improvement since stealth speed is generally handicapped by 30%. There have been plenty of times that I just couldn't reach the target in those ten seconds, due to AoE effects, Flare or other environmental issues. Fleet Footed also received a nice balancing change, moving it from a resist change on movement impairing effects to a duration modifier (25/50%) based on points talented to it. I am not fond of talents that have a large randomness to it (a la Blade Twisting) and that cannot be counted on to work ever. With the change to Fleet Footed it will now work every time and the more points you put into it (up to two) will always reduce the duration of any movement issues. One of our biggest issues is being kited around, or in PvE being stuck while a boss unloads on you. This will give you a passive 50% reduction in effect duration. Sweet.
So I mentioned Blade Twisting up there a moment ago. It's a lot better now that it's not tied to a few attacks but is now based off of any attack that causes damage. However, because it has a random element to it (even if it is 10%), I'd advise keeping away from it and applying those points to other things in that tree.
Finally, Vile Poisons and Riposte received nice buffs. Riposte used to be a talent in the Combat tree that would allow you to disarm your target for six seconds, PvP and PvE applications, after a parry and do 150% weapon damage to the target. Now we get a 20% slow on targets attacks to you, which is a better PvE trade off since many mobs don't use weapons anyway and cannot be disarmed. Vile Poisons has had its ranks reduced so you need to put fewer points into it to get the maximum 20% buff. That gives Mutilate builds an extra 2 points to put elsewhere, which is always a winner in my book.
So, dear reader, you've got a starting glimpse at what is in store for the class post-expansion, and for the most part, is good news. I would have liked to have seen more improvements around Stealth and Sap and certainly a for-sure fix for the woe that is Vanish, but I'll keep my fingers crossed for the next batch of class news that comes out.