Like many powerful currencies in the past, USD may fall to ground too, my question is will that effect BTC value? Or is it independent of all other real world or non digital currencies of the world?
Bitcoin is unique in the fact that it only fails when the community fails with it, in essence. As such, Bitcoin might just end up being extremely adaptable to whatever happens in the world, simply changing the currency it is pegged to from one to another, never really stuck to anything. Flavor of the century, if you may.
Savy investors may get involved with Bitcoin to protect their assets in case the USD starts to fail, and that would make the value rise, and then Bitcoin would end up pegged against something else. Basically a constant circle that never effectively resolves itself.