#1 - July 6, 2011, 3:09 p.m.
Blizzard Post
The season transition and introduction of new PvP items was different this time around, and we apologize for the lack of advanced warning.

The Season 9 set was removed today. The items available for purchase with Honor Points are now considered lower tier Season 10 items. They are still the same items from Season 9 in terms of aesthetics, but the item level and stats are slightly higher to ensure that the Season 10 honor gear has the correct item level relative to the Season 10 conquest gear.

It's likely this is how things will work going forward and we'll be sure to make that more clear when the next season transition takes place.

New basic transition flow:

1) Season X ends and rated play is unavailable; Season X gear becomes available for purchase with HP; CP is wiped.
2) One week later Season Y starts and rated play is available; Season X gear is removed entirely; Season Y introduces a low tier of items which replace Season X vendor items and are available for HP; Season Y introduces the new top items available for CP and rated play.