According to the roadmap, release is scheduled for March 25, 2025:
Outlook: Initial version of PST support in new Outlook for Windows
The initial version of PST support in new Outlook for Windows will enable users to open "*.pst" files (a.k.a. Outlook Data Files), read all e-mail messages within the "*.pst" file, and search e-mail messages within the ".pst" file. This initial support is limited to Mail items and is read-only. All Calendar, Contacts, and Tasks data saved in the "*.pst" files are still there, but they cannot be accessed in this initial version. #newoutlookforwindows
Microsoft 365 Roadmap | Microsoft 365