WordPress.com’s blog of August 13th, 2020 is entitled The Classic Editing Experience is Moving, not Leaving.
Read it for yourself. It appears to be saying that WordPress.com users will shortly be forced to use the new block editor. However, they can continue to use the classic editor functionality by using the classic block. In essence, when you open a post or page in the new block editor for the first time your content will be contained in a single classic block. If you want to use all the block editor facilities then you would use the “convert to blocks” function at that point. However, if you want to continue to use the classic editor functionality then you simply leave it as a classic block.
In summary, it appears that you are being forced to use the framework of the new block editor, but you can continue to use the classic editor functions if you so wish.
The blog says that WordPress.com users will receive an email when you are to be moved to the new block editor.
I will update this post if I see any further information on this subject.