WotLK - Release date / Talents / Abilities
You won't get a preview of them until a long time (misleading titles are evil). However we've got another confirmation that the 2.4 information are coming "soon".
Originally Posted by Blizzard Entertainment
I hope you aren't holding your breath on this as I don't believe any of this information is imminent. Information and updates on future content comes slowly so please be patient while we finalize and iron things out.
Details on patch 2.4 will be coming "soon" though.
WotLK - Death Knights
The idea was interesting, but quickly dismissed by Bornakk : You won't be able to "sacrifice" a character to get an improved Death Knight character by carrying over reputation, titles, equipment, or just getting a slightly higher level than newly created Death Knight characters.
[blizzquote author=Bornakk]If you want to "sacrifice" a character, you are welcome to role-play it out that way, but we don't plan to force this on players just to try out a new class. (
Source)
I see what you are saying, the option is there for you to role-play it in such a way, but we have no current plans for characters and their items (which I'm guessing is primary concern for this) to be converted into a Deathknight. (
Source)