I have this love-hate relationship with Notion. I m excited when Notion release the web clipper but can't use it to replace how I am using my Trello now. Notion has released a new version, and it excited me again.
I would like to see these features soon, in this order since I think the API might be the most challenging part.
Custom domain mapping
It seems like now day lots of people using Notion to publish product release / API doc/roadmap/ opinion; it will be best if they allow a custom domain to map the public page. I might even consider moving my blog & portfolio on it. Imagine after finish manages a project, move it to your portfolio page, really all in one.
The calendar view is excellent if only support the calendar feed, allow users to sync it with their calendar, I think this is what triggers me previously when I try to migrate my workflow on it.
I think everyone also waits for API to be released. Notion by itself already allows users to build many interesting concepts. Imagining once they enable developers to access the API, it will be lots of new creation appear.
I decided I am going to try to migrate to Notion again this month, use it within my workflow and see it is work.