Drang will be affected by the sunsetting, but I wouldn't say we'd lose Sturm because of it. In content where light level really matters, and using a lower capped level weapon is non-viable, then sure we'll lose that synergy between the two weapons, that they can both reload each other. But Sturm can reload any energy weapon so it's not like Sturm itself is losing any of its own abilities. I love using Sturm and Drang for hand cannon and sidearm bounties, but I can't ever see myself using them in any of the activities that sunsetting will really affect. Are they popular in Trials? I don't even know. They'll work exactly how they did before in anything else - Crucible, Last Wish, Dungeons, bounties and grinding, etc, if you wanted to use them there.