I started the roll-out on the 30th in the evening. There's not much of a delay for the October Bioconductor release, but for the summer release we first have to build the newest R version and then rebuild all conda CRAN packages. It's probably not widely known, but Bioconductor packages are only compatible with a single R version. For example, the ones being released now are not compatible with R 4.0 and will not be compatible with R 4.2, but will instead only ever work with R 4.1. This is regardless of what the metadata provided by Bioconductor package authors might say, the Bioconductor core team has requested this (there's actually not even a guarantee that packages built under R 4.1.0 will work with 4.1.1, but such issues are exceedingly rare). This is why there is a multi-week delay every summer.
On the plus side, at least we're not waiting for the first bug-fix release of R to start the migration anymore.
For Bioconda we've never gotten around to making a migration tracker. If you have a local clone of Bioconda, you can run
./scripts/bioconductor/rootNodes.py --sinceNDays 2 --rootNodes to get a count of the packages completed in the past 2 days and a list of the root nodes on the dependency DAG that still need to be handled. That's how I estimate the fraction finished (currently about 600 packages).
For tracking the status on conda-forge you can see their status page: https://conda-forge.org/status/#r410