Yes, all CS are open till 6:00p then only the CS in the land left open wil stay open...last year it was Frontierland/Adventureland so Pesco Bill was left open for the hour the park was closed. Years before it was Tomorrowland that was left open for that hour so Cosmic Rays was left open.
Before 6:00P everything will still be open. After 7:00p select counter services will be open; not all but most.
I prefer eating in a sit down restaurant for the hour the park is closed. This year we're eating at Tony's; in the past we've eaten at LTT, CP and the Castle.
CP, Castle and Plaza are open till 6:00p; LTT and Tony's are open during the party itself.