Is this allowed? I have a feeling the answer is "no" but I just wanted to make sure, because the demo is officially available, not a leak. Also, since there is such a long queue (at least for Models Resource) it wouldn't be processed until long after the game is out anyway.
I don’t see any reason why you couldn’t rip assets from it but yeah, they wouldn’t be approved until the game is officially out in all announced regions. As you pointed out, that’s not likely an issue for models given the length of the queue though.
If it's relating to the game I'm thinking of, you're better off waiting the two weeks for the game to officially release and ripping the models from the full version instead. Who's to say there won't be differences between those and the demo version's models? (It's not likely considering how newer games are, but you never know). Ripping isn't exactly a contest to be "first", after all.