#1 - Dec. 7, 2009, 4:06 a.m.
It's a little of both. Technically we have trouble altering inventory space in existing characters, and that would especially be true for the shard bag. We can do it, but it's a pretty high risk change when you consider all of the things that can go wrong. For that reason, we'd prefer to do it during an expansion when we have plenty of time to solve any unforeseen problems that arise.
On the design side, we'd prefer to unveil new mechanics that all work well together rather than make changes now that we'd just turn around and undo. What I mean is that we don't want to sideline soul shards even more for the next few months to the point where locks, especially newer ones, sort of forget about them only to bring them back in a big way for Cataclysm.