I just watched the new trailer and much to my dismay, the LXHG (League of Xehanort's Hammy Gentlemen) have indeed returned. I still dislike this turn of events because it contradicts the rules of time travel so they better have a damn good explanation.

 

That said, I apologize for constantly antagonizing people about this subject. I was an idiot trying to be smart and I now know that never works.

We can be sure that there will be a specific explanation for the reappearance of Xemnas and Ansem.  I have a theory that another time loop was started, and was based on the first time loop created by Apprentice Xehanort's Heart and Young Xehanort on the Destiny Islands.  Meaning, Young Xehanort may in fact have knowledge of what had happened previously, even though he stated he would lose all of his memories when returning to his own time.  If he were able to regain his memories while traveling through time for the first time, he would know exactly what to do when gathering his future selves/incarnations the second time around.

 

This could very well be a contradiction to the laws of time travel established in DDD, but what would be stopping any incarnation of Xehanort from lying about said laws?  After all, Xemnas completely lied about the presence of a heart in a Nobody, and was able to gain the trust/support of most of the original Organization's members through this lie.  What if there is at least one other element of time travel that has yet to be stated or explained, an element that makes the reappearance of past incarnations possible a second time?

How does it contradict the rules of time travel?

We can be sure that there will be a specific explanation for the reappearance of Xemnas and Ansem.  I have a theory that another time loop was started, and was based on the first time loop created by Apprentice Xehanort's Heart and Young Xehanort on the Destiny Islands.  Meaning, Young Xehanort may in fact have knowledge of what had happened previously, even though he stated he would lose all of his memories when returning to his own time.  If he were able to regain his memories while traveling through time for the first time, he would know exactly what to do when gathering his future selves/incarnations the second time around.

 

This could very well be a contradiction to the laws of time travel established in DDD, but what would be stopping any incarnation of Xehanort from lying about said laws?  After all, Xemnas completely lied about the presence of a heart in a Nobody, and was able to gain the trust/support of most of the original Organization's members through this lie.  What if there is at least one other element of time travel that has yet to be stated or explained, an element that makes the reappearance of past incarnations possible a second time?

You're right that the Norts could be lying again but they also tend to be quite truthful so we just don't know. The only information we have to go on is the little bit we got from Yen Sid and what the Norts say, there could very well be more rules to time travel than we're told but until then we have to work with what we have. Now the question is who would set up the second loop? Ansem had gone into hiding after sending Young Xehanort into the future so he couldn't have sent him forward again with new knowledge.

 

How does it contradict the rules of time travel?

As I said above, when Ansem goes back in time to send his younger self forward, he goes into hiding on Destiny Islands until its destruction some 60 years later. He then rides the wave of darkness to Hollow Bastion where he subtly manipulates the Disney villains and then possesses Riku, at which point he's picked up for his trip to the future. Because he passed his time powers to Young Xehanort and has gone into hiding, there is no one there to send YX on another trip to pick up his selves again which is why Ansem and Xemnas being at the Twilight Town mansion makes no sense and contradicts the rules.