"What is going to happen with our old legendary items?" is perhaps the hottest question that gets asked at least once everyday since the beginning of September. And we get told exactly the same thing every week on their Cord of the Rings stream: "Keep everything and we will let you know when we decide something."
We don't know. We still don't know. Cordovan once stated that he could tell us to use a relic removal to remove the relics from the old LIs and refine them, but what if the only thing that converts is the scroll? The producer stated that they are working on a list. These things will be rolling out gradually.