If Anthem wants to have the long legs of something like Diablo 3 or Path of Exile. Introduce Challenge seasons, do something similar to your difficulty scaling, but make it similar to the difficulty scaling, just make it a separate character each season. Then each season introduce a different mechanic either to mobs or to the javelins themselves. This could be something that could be a simple change initially but then could get more and more complex as the seasons progress. Have a leader board for tracking something, I am not quite sure what you could track. But at the end of the season you could have some kind of cosmetic reward for the top players.
This would probably satisfy a lot of the players who burn through content quickly and look for the next big thing. This could certainly be used between major content drops. I understand this is blatant rip off of D3 and PoE, but they basically ripped off of each other so..
I would imagine something like this would get brought into the game. I haven't heard one way or the other, but it would be cool to have something like this. With the Shaper Storms, the world will be changing regularly, so that will also help to keep things fresh.