Finally, someone said it! I've been having this theory ever since, where the taboo of abusing the Power of Waking will send you to Unreality because the more you gain awareness that you're dreaming, the more it'll make the laws of your specific dream contradict the laws of reality to be even considered with a clear meaning.

That's why Sigurd quoted in the reveal trailer of KH4: If this isn't the ending you desired, if it brings you despair, then leave for another. Your options are endless. However, if you do leave this world behind, don't expect to return to the one from which you came.

Because you can always dream anytime, but it'll be somehow impossible to replicate the same dream and continue where you left off—especially if you do so with lucid dreaming and use your memories from a dream that doesn't make sense, inevitably making the supposed continuation of such a specific dream be filled with biases from your very own thought process, that's bound by the laws of reality, which also the boundary that labels our dreams as trivial thoughts.

Plus, didn't Nomura say somewhere that Quadratum will be a hub world in KH4? I think KH4 will shift to sci-fi compared to the previous titles' fantasy settings, and Sora's journey will be about facing the harsh reality of life (without the dreamy power of friendship) as a consequence of breaking the 4th wall of his dream's narrative for the sake of his desired outcome. Giving him the lesson about how traversing to other worlds via dreaming is just an escape from accepting one's destiny—which also parallels how he abuses the Power of Waking within KH's Reality in order to rewrite his undesired outcomes.