But not broadcast as such. Here is why:
There’s a role in here called “HD Editing”. This role is also present in shows like Gundam 00, the new Fullmetal Alchemist, .hack//GU Trilogy, etc. Shows like the first season of Haruhi, CLANNAD, Kanon, and other shows animated in SD do not have this role.
Now before you say anything, none of the TV stations are airing this in HD probably on part of Kyoto Animation’s. It’s likely that there will be a Blu-ray set for the second season (I doubt they would do the first season, and if they do, it’s likely going to be a resize like AIR).