I am assuming everyone will meet in or around Caemlyn. Mat is already there and will likely head back there after Moraine's rescue. Perrin now knows Morgase is his lady servant I suspect he will also head to Caemlyn soon as well (likely Traveling). Rand, obviously can go there whenever he wants, but someone will likely tell him that Elayne is pregnant and he will go to her, or he sill be in the area dealing with the Black Tower.

In any case though, I think we could see most of the main characters in Caemlyn fairly early in the next book.