A few things…..when they say “can’t say,” to me that means they have a chance of addressing it at some point. They will tell us “no,” if they won’t, like the well for instance and the fates. So with that in mind, when they say things like Maleficent and Lily are not forgotten, that makes me think they still may go back to that. When they say “can’t say” for whether or not Merlin created the quill, that’s also exciting because that was an answer I never thought we would get.
Or it means that they haven’t come with an answer yet. If they say “no” it means that it won’t be address. If they say “yes” then obviously it means that it will be addressed. But “can’t say” either means that they won’t say for spoiler reasons or can’t say because they haven’t thought that far ahead and honestly don’t know what they’re going to do with ideas that are now laying scattered around the plot of 5 seasons.