Larian Studios Forums Divinity - Original Sin Divinity - Original Sin - General DLC, or official mods?

I haven't had my ear on the ground about this game long enough to know, but have there been any buyable extensions to the base game that have been announced?

No, nothing has been announced yet, but Larian has said previously that expansions were a possibility.

A larger parch is expected next month, which will at least add another 2 companions.

More companions yay! On a side note I don't even know where the hall of heroes is at so don't know where the often discussed henchmen are.

End of Time, it's the first portal that's opened near the weaver.

None of them are open

The hall of heroes will be opened the second star stone you find (the first opens the observatory portal). Both are available fairly early, once you get to Cyseal. One you can not miss if you follow the murder investigation; the other there could be a delay, if you hold off deciding something (reminiscent of a Divine Divinity quest, though there is no DD-like solution in D:OS) or advance the murder investigation too far and miss the first opportunity.