Well here are my predictions, might be totally off, but hey i might just be on the mark here... xD
Scholar Proffessions:
1) Elementalist
2) Necro
3) Mesmer
Adventurer Proffessions:
1) Ranger
2) Assassin
3) Mariner / Swashbuckler / Pirate
Soldier Professions:
1) Warrior
2) Gunner / "Engineer"
Yeah my two suggestions are totally unfounded, I know! But I don't care. I think there will be at least one or 2 new classes introduced in Guild Wars 2. With the advent of new technologies and weapons, this wouldn't be that far fetched.
Mariner / Swashbuckler Class - Cutlass, pistol, dual wield (Akimbo) pistols, some other weapons probably a crossbow (saw one in screenshot with Charr that has blade attachment - melee attacks or counters).
Lots of water and explorable areas under water in Guild Wars 2, so Mariner profession not that far-fetched...
Gunner / Engineer - Uses guns and ranged weapons with some melee weapons and probably a dual wield of some sorts. Also a crossbow as explained for the mariner.
Maybe baazoka-like weapon.
Also saying that it is or isn't in the books being released doesn't guarantee it will be in the game. Granted I really think the Mesmer and Necromancer will be in Guild Wars 2 and that the Assassin will be coming back as well.
Paragon, Dervish, Ritualist will probably be introduced with later expansions or campaigns. With maybe an extra profession.
That's my prediction man I hope I'm right