when the quilt is actually washed in a washer with detergent the pencil should wash right out- as for the ink- that ones a bit more difficult. grandma's spot remover is about the only thing i know of that might-
always test what ever you are planning to use to mark a quilt- even if it came out of the last one---always test
pencil and chalk are usually the easiest- but there are lots of special marking tools out there- ones that disappear with water, with air, with heat (others set with heat- or water----always read the instructions for the tool you choose---and again---test)