Thanks again for your help with the 6.4 Calc Guide, it is much appreciated.
I'm delighted to hear that you are interested in helping out with the 7.0 Calc Guide. If you visit the The Document Foundation’s wiki you will find that the planned software release date for LibreOffice 7.0.0 final is August 6th 2020.
Have you downloaded a version of 7.0 to try out? If not it would be worth doing so, possibly as a parallel installation so that you don't need to delete your current version of 6.4 yet. I use the Separate Install GUI to achieve this - see https://wiki.documentfoundation.org/SI-GUI.
The Calc section of the Release Notes at https://wiki.documentfoundation.org/ReleaseNotes/7.0 will give you an idea of what's changing at 7.0. However that won't be the full story as not all software changes find their way into the release notes - we will only discover some changes by comparing the appearance and behaviour of the 6.4 and 7.0 Calc software. If you do experiment with the 7.0 version of Calc, please keep a note of any differences that you notice.
When I've finished publishing the 6.4 document, we'll be able to move forward to the 7.0 update.