  The notion that any Aiel could have re-entered it. Recall the prohibition (I fought for this idea back when the books came out) that they were not to enter the columns a second time, iirc. It's possible that the Wise Ones know of this or passed down a prohibition, or even that other Wise Ones had entered a second time, or that this is part of the Wise Ones training later on to return to Rhuidean again.  If other Wise Ones had seen their own blood/mw future, it would make sense as to why they are very concerned about the Remnant of a Remnant. And wait...hmm...ok, while I use Dreamwalking as the reasoning for their interest in Aviendha...if other Wise Ones had seen the future...then Aviendha would be IMPORTANT indeed. Ok, I'm adding this to my theory. :)  I believe whatever happened with the columns, they were built for a variety of purposes and could be attuned to both past, present and future blood/mw-visioning.  