If i remember correctly, egwene dreamed about black tower demolished 3 or for times and then there was another one again (or at least it was sth. like that) 2days ago, I finished the last book and i have been thinking about this... Any idea?

It was probably referring to the turmoil that was caused by Androl and the others overthrowing Taim, just like Elaidia's foretelling. It would have to be either that or something that happens well after the series ends.

The fight with Taim in the BT is probably one, another might be the Seanchan destroying the BT from AVI vision.