You're right, it's just a tech demo. But we can make some deductions based on logic (and a bunch on speculation) and there are some clues. To wit:
Since they've been listening to feedback and there's clearly a return to classic art & classic music, it would seem remiss and out of place to continue with the more modern gameplay mechanics. So: (1) listening to feedback (2) classic art, (3) classic music ... seems to me if we follow what they've shown, the logical conclusion would not be Spartan Charge & Ground pound. Now, the Warthog and Battle Rifles the Marines were carrying were the newer versions while the Marine design as well as Chief and the Pelicans were classic, so ... perhaps a mesh of modern and classic mechanics. Perhaps sprint, thrusters, & clamber? Perhaps these assets are all placeholders?
So the next logical step is to conclude that we simply do not have enough information to make any judgement on the gameplay based solely on that. But it is pointing in that direction. At least enough to speculate on the internet out of sheer boredom. Which is all this is. How's that for saying "this is all a bunch of 'what if's?'"?
As for clues: the runes or characters carved into the cave wall and the stone ring structures ... remember the Halo 4 terminals when the ancient humans were being kept on the rings before being transformed into Prometheans? I think we're seeing their ruins. Perhaps that explains the ruins on Delta Halo as well. Though, I doubt they built those gondolas, so maybe Delta Halo wasn't them.
The screen inside the Pelican cockpit says "2560", so we know this will take place roughly 2 years after Halo 5. There's also a poster that says "Fight For Her", as seen in Combat Evolved and the MCC version of ODST. That poster was relevant during the Human/Covenant War, which ended in 2553, so what's it still doing in a pelican in 2560? So perhaps there's a canonical explanation for the classic Pelican: it's not just an artstyle retcon, it's old. Why are they using a pelican that apparently hasn't been used (or seen an interior decorator) in 7 years?
These are clues that, while not telling us exactly what's going on, might give us an idea of what kind of universe we can expect. Unless it's all cut & replaced, who knows? It's still early in development. It's just fun to pick it apart & speculate.