Based on our current understanding of physics and evolution then I would think it applies quite literally universally. For life to exist it needs energy, energy can be transferred from one place to another and as we understand it there cannot be an infinite energy source. Therefore with a finite energy supply there has to be competition and as such Darwin's evolution.
This is discounting things like eugenics or immortality (whether 'real' immortality or something like transferring your consciousness in to a clone).
On an OP point though, personally I think with the number of planets that have, do and will exist there will be other intelligent life within our universe. However, the more interesting question is whether there is intelligent life out there right now and if so what do we need to do to have the technology to get there.
You hit the nail on the head with "current". Science is evolving too and we're always discovering new theories, modifying old ones etc. Was once a time when people believed the universe revolved around the earth and so on. We're only just beginning to get to grips with quantum physics and we've barely begun with understanding Dark Matter. Our knowledge is far from complete. So it's possible the Darwinian model, as applicable as it is on Earth, might not be the only way life can evolve elsewhere. That said, I do agree it's likely to be a model that's replicated elsewhere.