Here's a headcannon from bookworm7713 thanks for the submission.
One that I have is that Dan is no longer a possible future for Danny. Why? Because I believe that the when the Disasteroid hit Vlad at the end of Phantom Planet, it killed him. I mean, if the crash didn't kill him, then he would have at least reverted to his human form, and since he was in space, that definitely would have killed him. Therefore, Dan cannot exist, since he's Danny AND Vlad's ghost halves combined.