As another data point: I wasn't notified either. I didn't have it when I first read about Canvas here earlier but coming back to the topic now I do have the feature. This is for a Teams account, the post says Plus and Teams are the first to get it rolled out with Enterprise and other in a week.
The easiest way to check if you have access is it will appear as an explicit choice in the "Model" selector.
I wasn't. I saw this post on HN, opened a new tab for ChatGPT, and saw that I had access to the model. I assume it's rolling out incrementally over a few hours to all paid users.
Thanks, I found that I had access too, on the web. Just open up the chat gpt page and use the model drop down at the top of the page.
You don't get the new experience until you give it a prompt though, which is kinda weird.