A week ago, I took a look at the test server pricing on existing items, in order to determine whether players who current have emblems, stone keeper shards, etc should buy now. These prices apparently were not final. In particular, heirlooms are now going to be much more expensive, and PVD advises readers to buy their heirlooms ASAP.
The Wintergrasp side is even worse; prices on these heirlooms increased by 6.79-fold. This appears to have been part of a broader sanity check pass on new honor point pricing, so further changes may happen. Level 60 and 70 PVP gear prices have decreased dramatically, probably to account for the fact that new honor points are more valuable, and therefore will be awarded in drastically smaller numbers. The old PVP mounts have also had their prices slashed 4-fold, and now seem more reasonable compared to the other items we can see.
The good news is that Argent Tournament heirloom prices have not changed. Though this could change in the future, my gut says that it might not. The tournament uses a separate currency that is only available through the current (level 80) quests (and one heroic dungeon). An item that costs 60 seals will still require you to complete 60 daily quests, because there won't be level 85 daily quests that award 3 seals. Also, unlocking the vendor to spend these seals requires completion of a lengthy daily quest-gated rep grind, and there's no reason for Blizzard to discourage players from signing up for this if they really want to.
Prices could change again, but my advice to readers is now to buy any and all heirlooms you can afford if you have any interest in using them. The worst thing that can happen if you do this is for you to end up with a full arsenal of heirlooms. The alternative is a real risk that these items will be harder to obtain in the future.
I've got several hundred emblems on my mage right now, which will net me either half a dozen heirlooms or a single piece of patch 4.0 level 85 dungeon gear. The heirlooms will stay with my account indefinitely, while the gear will presumably be trashed in patch 4.1. Frequent dungeon runners will still end up with heirlooms because of the hard cap on Justice Points, but these players have even less of a need to have a piece of gear waiting for them as a reward for past efforts.
Finally, anyone looking to cash out Stone Keeper Shards should bear in mind that these can only redeemed when your faction controls Wintergrasp. Don't wait til the last minute if your faction loses the majority of Wintergrasp battles.