For those of us who can't watch the video, mind giving a rundown of what you are worried about?
Sorry if it's a problem with the link, I've been having issues with it.
Basically, in the video he explains that the first 2 Kingdom Hearts games on PS2 were made by the Square Enix "Tokyo" team, and Birth By Sleep and Dream Drop Distance were made by the Square Enix "Osaka" team. However, KHIII is said to be currently developed by the Osaka team. He continues to say that the games made by the Tokyo team were better and more skillfully made than the ones made by the Osaka team, and not just because they had a bigger budget.
He says that the games made by the Osaka team were unbalanced. He uses Thunder Surge from bbs and Balloonga from DDD as examples. He says they're the best in any situation, even better than commands that fill up more space and are harder to obtain.
He also says that the regular keyblade combos felt more connected and satisfying to pull off than the combos you make in bbs and DDD. When you mash the attack button in KHI and KHII, it feels like a string of attacks and are fluid. But in bbs and DDD, they're more disjointed and it seems like the character is hesitating after every attack going into the next one. In the KHIII E3 trailer, you can see the aerial combos act a lot like the ones from bbs and DDD - disjointed.
The boss design is also a problem, as well as the different strategies in fighting them. In the data organization XIII fights for example, there are different ways to get around them, they have their "revenge values", and once you have them staggered, you can pull off a few combos. But, with the boss fights in bbs and DDD, it seems like you have to dodge roll over and over again, waiting for an opening and then using a command when you have the chance.
Anyway, I'm just paraphrasing. He words it much better in the video, but those are the main concerns.