I don't know. Honestly, I think the Division is better with just PVE, honestly. I never really thought the PVP was all that great or fleshed out, and the game is just better suited for players working together than against each other. Just my opinion though. So if they were to do a Battle Royale, I'd have two main concerns aside from that.
One, would developing a game like that take resources away from the main game? I'm sure they'd have separate developers working on it or whatever, but if it becomes the next Warzone or something, (I don't think that will happen, I'm just being hypothetical here), then would Massive move devs off of the Division 2 to support Heartland, which might mean we see content less frequently or in lower quantity than before? I'm not sure how big Massive is, I'm sure they have lots of people, so this is just a hypothetical.
Two, I'd be worried that it wouldn't attract an audience. Now what I mean by that is that while Battle Royale is still very popular in terms of people playing it, there's been less and less coming out, because the market is pretty much full at this point. Between Warzone, Fortnite, PUBG, Apex, and a handful of others, there's not much room for another competitor in my opinion.
Maybe I'm a little biased on the subject, as I've never really been a fan of Battle Royale games. I've tried Warzone, PUBG, a couple others. Not saying they're bad or trash or whatever, I'm just saying they're not my thing is all. Maybe I'm wrong. Maybe Heartland will be the next Warzone, and attract ten million players and it'll be what everyone's talking about. Or maybe Heartland will be something totally different. We probably won't know anything until late this year when they announce whatever's coming to the Division 2, or maybe a little earlier, who knows.