I've been reading the new GI update and it's got me extremely excited for Skyrim. My normal playstyle revolves around being some type of Soellsword, and in Oblivion I already adopted I similar style to what has been presented in Skyrim; sword in one hand, magic in the other (i.e no shield).

From reading the update though it sounds like you must have a shield to block. From my interpretation it uses the "Offhand Button" (which will control my magic) to allow you to block with a tap, and bash with a hold. I can't see them including an extra Block button with that system in place, as it would effectively limit a shield wielders options.

I'm hoping I'll still have the ability to parry with a single blade, and that my interpretation of the article is incorrect. What do you guys think?

This is something I too would like to have answered.
I liked using a single short sword for my thief character.

I'm really not sure if they will have blocking for spell swords.

They said you can bash with a two-handed weapon - that implies weapon blocking. It'd be really weird if you could weapon block with a claymore but not with a longsword. The system will probably utilize three buttons - one for each hand and block. If you use a shield, the off-hand and block buttons do the same.