There's nothing technically wrong with updating, but I'm assuming that they'll want these new ones to fit right alongside the old ones during a run. To a kid watching these cartoons, they likely won't even notice it being more modern. I suspect that's part of the plan.
The thing is, though, the original ones did go through a lot of stylistic evolution over the decades, as I mentioned. You can pretty easily distinguish a cartoon made in the early '40s from one made in the late '50s.
Besides, they said in the article that they want these cartoons to be director-driven, which would suggest we're actually going to see a lot of variation in the visual and comedic style. This one may have been more of a throwback simply because it's a teaser.