That is a very good question. And I would like to answer that question from what I've observed thus far in the Beta. As with Relmstein, I think this is a question many of us have been wondering. In some cases we can see that Blizzard made design decisions ostensibly to correct some of the mistakes they previously made. So in large part, I think Blizzard won't make all the same mistakes. But in others I think they really have little choice because they have no impact on how people play in general.
Dynamic spawn system problems - I like the fact that Horde and Alliance factions have different starting zones this time around. And I can only hope that it does indeed help with the spawn issues Relmstein refers to. There just wasn't anything fun about running through parts of Hellfire Peninsula and having things spawn crazily around you. In fact it became downright tedious as you attempted to move into, then out of areas multiple times. My guess is that simply because there will be less people in a concentrated area this will be less of an issue, but time will tell.
Outdoor PVP objectives - I do not share the same opinion regarding how popular Halaa and the Bone Wastes were. Certainly at the beginning of the BC they were fairly popular, and then again attained more popularity when the daily BG quests were introduced. But I don't think they were anywhere near as popular as Blizzard had hoped they'd be. On my server I almost never see a battle over Halaa, and fighting over the spirit towers in the bone waste are always relatively small fights because frankly there just isn't anything worthwhile to buy with spirit shards. I am however, a little more excited to hear about the new outdoor PVP zone in WotLK because the benefit for winning is much larger scale and more robust. That essentially were the big problems with Halaa in Nagrand, and the Bone Waste in Terrokar. The benefits to winning were so small that even if you had interest at some point, it quickly waned. It looks like Blizzard answered this in large part.
Missing the leveling truce - I honestly don't think there is anything that Blizzard can do about this. They split the starter zones, so some of it will be cleared up. Yet without keeping the two factions completely separated you are still going to get to a point where you will enter "ganksville". And people who enter that zone at a point after most others have already finished leveling are going to continue experiencing the full brunt of it. And of course this point only has merit on PVP servers. If you don't want to be ganked, then play on a PVE server.
Raid blockage at Karazan - I remember this quite well, because it was a huge problem for guilds--including my own. Several arguments ensued initially because the core clique in my guild formed a team and everyone else was largely left out. We eventually were able to form a second 10-man raid team, yet there was a fairly large disparity between the quality of members which created even more arguments as team A went much further, much quicker than team B. Eventually the teams were broken up and members were allocated between the two teams again to make them a little more even at which point most of the problems were resolved. Yet even more problems crept up as we then attempted to transition to 25-man content in the very next dungeon. The transition from 10-man raiding to 25-man raiding is actually fairly difficult from the perspective of manning. The numbers of raid slots, and sub slots that you would typically have for a 10-man team are quite a bit different than one would have for 25-man raiding. Then factor in the larger problem in BC raiding that many of the fights in raids called for specific classes--who then were not needed (or even desired) in follow on fights. Take Gruuls for example. You would have 4-5 tanks for the High King, then only need 2 for Gruul himself. Raids would often bring 5 tanks to High King, then replace 3 with DPS for Gruul. Grumbling and problems galore.
My sense is that Blizzard has addressed this issue in part with their new raid philosophy. There will be 10 and 25 man versions of every raid so a 10-man team can continue raiding from beginning to end without ever having to change. Transitioning from 10 to 25-man raiding will of course require some modification, yet Blizzard has also dramatically changed mechanics in such a way so that specific classes are no longer required giving raid leaders greater latitude when forming their teams. Tanks in particular do much better damage now, so even if the number of tanks fluctuates between fights, you probably won't have to sub tanks in and out on fights. That alone should make people much happier.
Rewards for heroic dungeons - I think Blizzard failed miserably when they created the loot tables for heroics. There simply was little to no reason to even run a heroic, except for the badges. All the bosses, save the final boss, dropped the same loot as they did on regular. Yet the fights were much more challenging. Blizzard added in epic gems (not really all that better than the rare gems we were already using) after BC started but that didn't really change the central question of reward for risk. In WotLK there are different loot tables for Heroic dungeons, so this question I think is largely answered.
All in all I think Blizzard paid a great deal of attention to the problems they encountered--and created--in BC. And I think they fixed the vast majority of them.