I have not seen anything either. I would suggest clicking on "Help" in Canvas and then click on "Submit a Feature Idea" to officially make the suggestion to Canvas Support. That is the preferred method for suggestions since this community forum is more for community members to help each other. This post would help to gather feedback from other users, which could help in submitting an idea.

If you do submit the idea, I would consider the value in suggesting changes with some more specifics. You describe changing the look to be more rounded (I could see some spots where this would be visually pleasing). A rounded vs non-rounded look sounds more like a visual change rather than a change in how Canvas operates. While some might find this visually better to use, that difference would likely have little impact on making Canvas actually work more efficiently or make performing tasks and navigating any easier. I suspect you have other ideas for improving the look beyond just this, so you would want to provide those details when you submit the feature idea.

I do have a suggestion to enhance your idea. It would be an option in the settings for a course that allows users to switch between a "Classic" view and a "New" view after making some of the changes you suggest. I like the idea of updating the look in some spots, but some may like keeping it the way it is. This way, users have that choice if desired.