I'd love to see a wizard build based around necromancy, but I have a sneaking suspicion that they'll save that for a book built around a Shadow power source and not mix it with the arcane. Given that I'd guess illusionist is a good bet; I just can't see necromancers or illusionists either one as strikers.
I feel pretty sure they'll throw warlocks another pact, as well -- though god only knows what it could be -- but moreover they'll almost certainly give them a much wider variety of paragon paths, because warlocks have just about the fewest choices come level 11 in the game right now.