[Sijo]

Just for the record, there was something similar in the comics: The "Iron Curtain of Time" created by the Time Trapper in Legion of Superheroes: a barrier that prevented the Legionaries from physically traveling into their own future. The original reason for this was, I believe, to explain why the Legion didn't just go to their own future, find out what was going to happen, and then prevent it. In other words, a plot device. Note the barrier didn't prevent people *from* their future from visiting them or other eras, thought (as was the case with the Adult Legion of Super Villains attacking Superman.)

I'm not sure what happened with this later, though. It may have turned out that the catastrophic "five years later" Legion's future was behind the Curtain.

Anyway, I hope there is no big disaster behind the Wall in an updated IST; I'm no fan of such settings, not for super heroes.