Did Horizon have English subs on the BD? Weird. lol
I remember that Haruhi was released on BD in Japan with English subs and a BD release never came here.
Aniplex has just started selling their JP sets here, but for mostly the same price as the Japanese MSRP.
At this point, it's up to Funimation or Sentai and I'm not sure if either is interested at the moment. I'd love to be proven wrong though.
Yeah, there's been a lot of English subtitling on Japanese BDs lately, most likely because the US and Japan are the same BD region. You can find out which ones here
I own a few of them actually such as The Garden of Sinners
and the two Fate/Zero
boxes from Aniplex as well as a fantastic little sci-fi OVA called Time of Eve
and have Library War: Wings of Revolution
on pre-order. Importing from Japan will only make you poor though, not really worth it unless it's something you like a whole lot or you know the thing won't ever be picked up and licensed by anyone.