Well, there's nothing in the article to say that the 4e Warlock is exclusively evil. It's possible that the alignment may depend on the pact source chosen - Evil for the infernal pact, Neutral for shadow, Good(?) for wild. Alternatively, it could be Lawful for infernal, Neutral for shadow, & Chaotic for wild - or even no required alignment/source pairing at all (Chaotic Good character holding a pact with devils? Perhaps challenging to roleplay, but if the player can handle it, why not?). Point is, we just don't really know yet.
I do think it's pretty clear that the planar sources of the pacts are probably Hades for the infernal, Shadowfell for shadow, & Feywild for wild, & that sounds a more flavorful to me than the 3.5e assumed source + 1 option mentioned in the class text.