As a Catholic my own opinion on that would be that some protestants (probably most of them) can certainly be in state of grace and saved, though it has nothing to do with their "communion" ceremony.
In the case of some protestant groups like Baptists, all they're doing is eating bread and remembering Jesus death when they do it. That won't matter at all when they're in the afterlife, anymore than if a Hindu ate some bread and drank some juice while thinking about Jesus' death.
HOW they live their lives and IF they accept the one true God will determine if they are in a state of grace and saved, not their bread and grape juice ritual.
So which Protestants would not be in a state of grace and saved? you say that only some would be...