Be warned that the very end of today's edition of The Queue contains minor spoilers for the upcoming Ulduar raid zone. Everything is perfectly safe until the very last question, and even then the spoilers are very minor. Minor as in it describes a couple of the bosses found within the zone. It doesn't give away any story or plot. If you want your experience to remain pure, stop at the last question. If you don't care so much about knowing who you'll see in Ulduar, it's perfectly safe.
I warn because I love.
What is the deal with the Greymane wall in Silverpine forest? Is there an old raid set in there? What is on the other side of that monstrous wall?
The nation of Gilneas is behind that wall. At least, it was. We don't know if it's still standing. Gilneas is/was another Human kingdom that was part of the Alliance of Lordaeron. Genn Greymane, the King of Gilneas, never fully agreed with the Alliance's decisions and wasn't fond of many things it did, so he eventually said "nuts to you all" and built the Greymane Wall, locking his nation off from all of the crap that was going on in the world. Whether it was successful or not, we don't know. We haven't seen anybody from Gilneas ever since.
It's likely that they're all dead.
How much rep do you get for every run on level 80 instances wearing the tabard?
How much rep you earn via Championing a faction varies per dungeon. Wowwiki has a good list for them all that you might want to check out. Level 80 Normal dungeons only give around 500 reputation, Heroics give a lot more. On the low end is Azjol-Nerub and Violet Hold, those two will only give you about 1300 reputation. The high end is Ahn'Kahet and The Nexus, who each give you 2300 rep. Everything else falls in between.
Do you have any idea when 3.1 will be released?
When it's ready. Also, soon.
When I see the mount vendor in Darnassus, They have 2 quests to trade in old mounts. Is this still coming or olden time mounts?
That's a really old school trade-in. Way back in the day, epic mounts didn't have the models they do today. They looked exactly like the non-epic mounts, just with different colors. They didn't have armor or special decorations or any of that. When they added the new mount models, they put in the trade-in option for people who wanted to exchange their armorless mounts for one with armor. The armorless ones aren't available for purchase anymore.
Once every few months I see someone riding around with their armorless epic mount and I smile. That's the definition of old school right there.
Now, Minor spoilers incoming!
I'm a little confused about the Ulduar raid. Is the vehicle section actually outside the instance or not? The Hodir preview said it was before the instance portal.
Ulduar is an instance within an instance. When you first zone into the raid zone, you're in a massive outdoor area. This is where the vehicle portion will take place, and there's room for a number of bosses beyond that. When you reach the end of this area, there's another instance portal. This portal takes you to the inside of Ulduar.
So the vehicle portion is inside of the instance, yes. Hodir and the Iron Council and such are also inside of an instance, but not the same instance. You take a second portal to get to them.