Added this info to the first post.The Artificer is an arcane leader, and will appear in the Eberron Player's Guide (source). A playtest/preview version appears in Dragon 365.
Added to the first post a mention that the Forgotten Realms Player's Guide will also include a multiclass-only class for characters with spellscars (source).
Uh? Buh? Wth does multiclass-only class mean? Is the preview guy smoking crack or is the FR Player's Guide introducing some crazy new class system?
Don't know if this is 100% relevant as a "new" class but the Bazaar of the Bizarre: Treasures of Ashardalon article (http://www.wizards.com/default.asp?x=dnd/drbaz/20080707) mentions dragon pact warlocks. My best guess would be a spoiler for PHB2 or the Arcane Power book
Phaezen
It's been more or less implied that the Player's Handbooks would be about introducing new classes rather than adding to existing classes so far.My best guess would be a spoiler for PHB2 or the Arcane Power book
Phaezen