First off we have to define whether or not the changes we're being told about are 'negative' - in the case of a currency simplification, I don't see how it could be. The interview being discussed is Ion Hazzikostas talking about various things, and mentioning "Yes, we have plans to simplify currency" and explaining how the extra roll mechanic removes some of the pressing need for the currency catch up mechanic. That's it. That's all he said. He didn't say Valor points were being removed, he merely said that with the extra roll mechanic in place, there's less need for bosses to drop a currency so you can purchase gear if the boss doesn't drop anything. He even mentioned revisions to the extra roll mechanic if it became the replacement to the Valor catch-up system introduced in The Burning Crusade as Badges of Justice.
Considering that we've seen the Badge system develop from a one badge system to a many badge system (at one point we had badges of Justice, Valor, Frost, and probably some I'm forgetting) into the current currency system in Cataclysm, it's not surprising they'd want to iterate on it. As we've pointed out a few times here, currency in WoW right now is kind of wonky, and it's a safe bet if you've noticed something weird in the game, the folks at Blizzard have noticed it too. So it's hardly astonishing or consternating for them to discuss currency systems when directly asked a question about it.
The reason it's worth talking about isn't just the reason Bashiok mentions, but it's a valid reason to start with - is it worth warning people up front, getting people ready for the changes coming so that when they actually happen, they're prepared? Well, it's never going to universally work, of course. There will always be people surprised by news, no matter how hard you try to get that news out there. News doesn't just equally distribute itself as soon as it happens, and people's investment in information sources varies - one player can be saying "ugh, will they just shut up about the changes to CC" in guild chat, only to have the next player say "they're changing CC?"
But it's valuable still, because then the first player will explain the situation to the second. The player community is a larger and more effective information distribution network then you can imagine - far larger than the forum goers, or those that read websites like this one.
Furthermore, besides the idea of getting people prepared for a chance, informing them of changes in advance works in another way - it allows Blizzard to gauge where the community is on a given issue. And that's important - it's another information source for them, and it can lead to development and iteration of their design. Blizzard very rarely scraps a design change based solely on it, but the discussion of how important soloing older content was to players has definitely led to an emphasis on how player power relative to outdated content won't be affected - Blizzard going so far as to introduce a buff that will make sure it will be possible. If players don't get to have those discussions, Blizzard (and therefore, the players of the game indirectly) can't make use of them in the first place.
Our expectations of the game are important, and the discussion of those expectations is useful. It doesn't bring immediate change, but it does give Blizzard more information to go on.