Agree on the lack of communication - the message center in my tenant says this is medium impact for me, despite Project being the only additional paid subscription. Yet a minor Outlook for the Web change is flagged as High, yet I never use that product. The published lifecycle for Project Online hasn't yet been updated, and no banner on my PWA site - and I was also able to create a new one just yesterday with no indication of the pending retirement. Plenty of other marketing and support web pages not updated. Not the comms you'd hope for from an apparent billion dollar business in the largest software company - but the Project Online product was not the only part of the Planner/Project ecosystem that lacked investement.
From the partners, there are quite a few that could be described as modifications of the Accelerator, but also many that go a great deal further. There are also some that took a different approach and aren't as tied to the Power Platform.
My biggest concern are the customers who may not live on LinkedIn, don't visit the TechCommunity (or maybe only looked at the Project blog and not Planner) and may not have access to the Message Center in their tenant. Hopefully the message will get to them somehow.