I assume that it is in, but I think that it will come into play even less than it did in 3e... and that's saying something.
In 3e, players were encouraged to hold a ton of items as they needed every equipment slot filled to gain advantage over the monsters. For every moderately leveled adventuring NPC that you killed, they usually had all/most of their slots filled which creates lots of loot/weight to lug around. (Albeit that Bags of Holding kind of negates the need to track much of the weight.)
In 4e, as we know, there are many fewer equipment slots which, by my logic above, should mean less treasure being awarded and creating less weight to cart around.