I'm not expecting any arc for Iris at this point, however I expect she'll a cameo in some form. Most likely she'll be watching Ash compete in the Kalos League on television whilst in Johto. Either that, or perhaps the opposite, similar to the end of Sinnoh - after the league Ash catches Iris on television in a battle with the champion Diantha/Drake or a Unova/Kalos Elite Four member.