I found it, actually. It was in the 4/10/2020 Shadowlands Lore Interview with Steve Danuser and Taliesin and Evitel. Specifically, Danuser, when asked if the remains of the sword would "disappear from Silithus," replied "[t]he sword has a part to play in something to come" with no real further information. Since this was an interview about Shadowlands lore, it was generally assumed that this "something to come" would be part of the Shadowlands story, although Danuser's answer is open and evasive enough to mean it's just fuel for a future story they plan to tell, somewhere further down the pike.