I'd hope a weight based system will not be implemented.
I fear this would end up being even more tedious because when you're on a looting run, you would get cluttered up in two ways, not only because of limited inventory slots, but also because of weight.
My idea was about somewhat mitigating a "filled too fast" inventory. A weight system seems to even add to the already existing "problems".
The limited stack sizes now already do more or less the same thing as "weight" in priciple, and these sizes are already sometimes weirdly chosen, just for keeping the game playable...what could it do better when you call it "weight"?