It's all about forward looking statements, and in general companies don't like to make them. If they make them and then things happen differently, it's possible for them to get sued. That's why if you look at the BlizzCon announcement page, for example, or any press release, there's gigantic legalese attached that basically says "Blizzard is not responsible if these statements don't come true."
Now does saying something like "Mount changes come in patch 3.2" and then it gets delivered in patch 3.1.4 constitute a breach of some apparent contract that a judge could rule against Blizzard with? I don't know, and I don't think anyone knows for sure.
But no one wants to find out.
The other side to the coin is that with 11.5 million players, you're bound to make some large group mad if you say you'll do something and then change your mind (even though your decision not to go forward with the plan is perfectly reasonable). The folks at Blizzard are real people, despite their promises of ponies, and no one like to make 100,000 people dislike the game they play so much. Even if that 100,000 is just a rather small fraction of the overall community.
"With the recent changes to mounts, how will the mount quests for Locks and Pallies be done? I'd like a Feat of Strength for my Pally to match the one on my Lock and Druid. Will we need to not buy the class mount from the trainer, and wait until level 60? Can we still do the quest if we have the mount already trained? What's the plan?"
I'd assume the quests will remain at their original levels because they're tied to dungeons of those levels. You can do the quests whenever, even if you have the mount. They're a fun and unique thing about WoW, and I recommend everyone tries them all out, even though they're not required anymore.
"If Blizzard is not going to let us fly in the old world, how about they give us faster land mounts (like epic flying speed, but on the ground). Seems like an obvious idea. Has anyone from Blizzard ever commented on this?"
100% speed boost on the ground is pretty fast. Remember that traveling by ground you need to navigate terrain and other obstacles. By air you can pretty much go as the crow Medivh flies. Blizzard has said before they don't want the epic flying mounts to go beyond the 280%/310% increase they give now, and it's not hard to draw the conclusion that they're probably okay with the land speed as is.
Out of the realm of possibilities for the land speed mounts to increase in speed? No. If they do, should we expect a major jump? No.
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