Remember that the vanilla quests were designed between 2002 and 2004 -- that wasn't anything like the gaming era of today. That was "back in the day," when EQ was a major player and the hardcore mindset was considered the standard model to design a game towards.
Today, it's all about a mixture of casual and hardcore, and one of the primary ideas of a more casual gameplay is not to have insane breadcrumb quests sending you across the majority of the world (and then do that again and again, because all the quests are the same). So at the time, Blizzard was thinking correctly. And today, Blizzard is still thinking right. It's a major strength of the company to adapt its game design and admit that what it did five years ago isn't up to today's standards.
"How will we know when we can actually go help take back the Echo Isles/Gnomeregan? I am really looking forward to these events!"
We don't know exactly what will signal them, but if past events are any indication, we'll get some in-game announcements around the capital cities -- probably some NPC yelling about it. Of course, there'll also be a lot of new quest givers and everything.
WoW.com will let you know the moment it starts, or as soon as we have any firm indication of when it is scheduled to begin.
"Can non-goblins get into the goblin starting area where you drive around on a hot rod?"
Nope. That area is a specific zone/phased location, much like the death knight area is. It might be possible for a person to summon another player there via the Recruit-A-Friend summons, but we don't know about that yet. Pretty much, it's goblin only.
"Now that information on the new talent and mastery system has been released by Blizzard, are the first four Cataclysm talent trees (hunter, shaman, rogue, druid) previewed thus far still relevant? Or are they being scrapped?"
The talent previews are still relevant. They represent the individual ideas that Blizzard has for the class, and from my understanding, many of those talents will be carrying across into the new trees. The thing is, though, this is beta and anything (as we've seen) can happen. So don't worry too much about talent trees until the release date nears and we have a more firm idea of what the talents will exactly be.
And as for that release date ... we still don't know, other than some time in 2010.
Have questions about the World of Warcraft? The WoW.com crew is here with The Queue, our daily Q&A column! Leave your questions in the comments and we'll do our best to answer 'em!