Will we be able to do the BC heroics for the achievements after Wrath comes out?
Yep! Just like you can still earn achievements for the Classic dungeons in The Burning Crusade, you'll be able to do the BC dungeon achievements in Wrath.
Does Culling of Stratholme grant Keepers of Time reputation? If not, is there a new faction associated with this instance?
Last time I ran this dungeon, it wasn't awarding any reputation at all. That may have changed since then, but a peek at Wowhead and Wowwiki doesn't show any associated reputations.
Here's a question for ya; Are the pvp items for the different factions (Horde, Alliance) going to look different again or are we all going to be wearing the same duds? The current "Various pieces of Arena gear for all..." system kinda blows the whole Armies at war feel for me.
The two factions do indeed still share Arena sets. Sorry to disappoint!
How soon into Northrend can we start getting rep for the endgame factions such as the Knights of the Ebon Blade or the Argent Crusade? Do they have fairly early quest areas or do we have to wait for higher up dungeons to get any rep for them?
It largely depends on the faction. They're spread out a bit, like the Burning Crusade factions. The two you mentioned are primarily later in the leveling cycle, though. You start seeing them in force in the upper 70s. You'll see a few Argent Crusaders before that, but not a ton.
Will Outland and Shattrath become obsolete for level 70+ once the expansion is released? Or will there be something required in Shattrath forcing us to return there, similar to how the Auction Houses are only in pre-BC content.
Aside from a few quests that take you back to Shattrath, I haven't seen any major reasons to return to Outland. I guess you might be going back there to finish up achievements if you haven't done so yet, and I have the Blessed Medallion of Karabor from killing Illidan so I use it from time to time to get at Shattrath's portals if my Dalaran hearth is down. I can't go straight to Dalaran from Shattrath, but I can get to the Stormwind Harbor at least. That's really it for Outland, though.
Are endgame raids/instances in Wrath really that easy? I've been hearing from numerous beta testers and other bloggers that everything is just so darn easy. Any testers have any input on this? If this is the direction Blizzard is going with WoW, I'm not seeing any reason to stick around.
So far things are pretty easy, but remember that only the first 'tier' of raiding is in the game, more or less. What we have now is essentially Wrath's equivalents of Gruul, Magtheridon, and Karazhan. Only difference being they're appropriately tuned as entry-level raids unlike early iterations of Magtheridon.
As we get deeper into the expansion, things will surely get harder. We don't have Ulduar yet, and there will be
another raid between Ulduar and Icecrown, if not more than one. Things will get harder, though perhaps not Sunwell Plateau harder. That was a bit much.
And fungus, buddy? I was just kidding, I promise! Will you be my valentine?