Thank you for your patience. We now have Bioconductor 3.11 running on all three platforms (linux, mac, windows) as seen on our daily build report.
http://bioconductor.org/checkResults/3.11/bioc-LATEST/
We encourage all maintainers to monitor their packages as there have been many changes with R 4.0.
We realize that many packages currently fail on mac and windows because of missing dependencies. Unfortunately many packages from CRAN are not available yet in an R 4.0 binary form. When these packages become available, the build system will install them automatically and these types of ERRORs will clear on their own. Until the binaries are available there is nothing more that the Bioconductor build system will do. We appreciate your patience with this and we will get packages dependencies installed as soon as they are available.
Thank you
Bioconductor Core Team
Is there a rough estimate for the R 4.0 release date yet?
This information is usually posted in the 'Release plans' section of http://developer.r-project.org when it becomes available. So the current best guess is 'spring'.