Now, I for one, am glad that shadow is having their utility being toned down. I think most people here can agree that they currently are too strong in PvP as they offer a bit too much of everything right now.
However, as Yvaelle said, just nerfing shadow priests is not going to change a lot, frost mages, resto shamans, sub rogues, etc, also require some nerfs to make these changes actually worthwhile.
That being said, don't go crazy about these changes until the full patchnotes are released. Blizzard knowing, they look at 1 class at a time, so unless you suddenly start seeing frost mage buffs, I don't think there's too much to worry about right now.