This is exactly it. Maresca's preferred style of play demands the goalkeeper can step up and effectively become a central defender when we're in possession. To do that, he needs to be very comfortable on the ball. Neither Iversen nor Ward fit the bill in that respect, but Hermandsen definitely does - he's known for being excellent with the ball at his feet as well as being a shot stopper.
At least one of Ward or Iversen will go, possibly both. I feel for Iversen as he's been patient and did ok when he came in last season, but he's not a ball-playing keeper so therefore is not likely to feature under Maresca.