I've heard rumors of dark elves and necromancers being added in BG2! Is this true? PLEASE!!! I must know!!!

Necromancer is a specialist wizard, and nothing new. You've been able to play necros in the original BG.
And no, you won't be able to play Drow. You will go to a Drow city in the course of the game, but that's about it.

you can create an evil elven necromancer with dark skin and white hair though, it comes pretty close, except the sun won't hurt his eyes....

Just use a character editor to give the appropriate magic resistance and innate stuff.

I don't mean the specialist wizard, I mean an undead wizard with awesome powers.

An undead wizard with awesome powers? That's not a necromaner, that's a lich.
Necromancer is simply a specialist wizard dealing with the dead.
Necromancy is one of the most restrictive of all spell schools. It deals with dead things or the restoration of life, limbs, or vitality to living creatures. Although a small school, its spells tend to be powerful.
But it's practitioners certainly aren't required to be dead. ;)

I'm talking about a necro class, not a specialist wizard. Will there be one?

There is no necro class. This ain't Diablo heh.