First of all, love the game. I have no doubt Illfonic will continue to tweak the game and make it great!
That being said, something that I think will give the game longevity is plenty of customization. Adding more aesthetic options continually helps to create unique and personal Fireteams or Predators. It gives Ayers something to work towards and keep the game fresh. Perhaps adding a new class/perks/gear/weapons down the road will open up new options as well.
What would you like to see?
Keep up the good work Illfonic