LOL, I loved the lizardmen argument.
I think that serious changes are higly unlikely at this point. They had 4-5 years for tinkering with animation/GFX and making it better than Oblivion after they got the first reviews of the game.
If they didn't do it until now they won't change it. If they really did make serious changes then why show the presentation based on old stuff? I'd drop everything else and make a decent new show for the people waiting for my product. If I had a car company and wanted to show my new car it to potential customers I wouldn't smear it with shit and tell everyone that this is just a presentation and the ones you'll be able to buy will be clean. It's just bad publicity. Even though Beth seems to recieve a lot of good press and creates a lot of hype I doubt that they would base the presentations on something very different (and worse than) the final game.
AND If they did they should start the demo by saying that this is the build from year ago, animation might be lacking, we're on the verge of release and had other things to finish than to redo it, blah blah blah. Which would seem kinda half-assed as well, because 2-3 months before release you are probably very close to getting the physical copies of the game and maybe making some final touches to the code. Which in turn would allow them to use the actual "almost final build" of the game for the presentation.
tl;dr:
The point, is that if the game comes out on time there's about 99.9% chance that we'll recieve something that closely resembles what we saw on the demos.