When would S.Korea has P4W?
Currently S.Korea and France doesnt have new p4w.
Why is that and when can S.Korean tenant can use new p4w?
South Korea and France will have access to Project for the web on April 6th. If you are the Office 365 admin for a tenant in one of these geographies you should see a post in message center about this. You will need to opt-in to Project for the web.
Roadmap recently became available in these regions. Again the Office 365 admin will have to opt-in. This article has more information https://docs.microsoft.com/en-us/project-for-the-web/turn-project-for-the-web-off