Elyas Machera will be back. Robert Jordan won't just forget about him he was a warder who has killed warders and is wanted by Aes Sedai. My guess is that he got involved in the events following the Aiel War and knows what happened that is so hush hush. He might meet Elaida who also knows what happened then she says so at the begining of ACoS in the prologue when she is talking to Alvirian. So Elyas will be back.