BIOS-based systems make up a miniscule minority of the current
market.
Pretending otherwise is delusional, and delusions are no basis for
technical decisions.
- Solomon
In terms of physical x86 systems, you are right that UEFI is the overwhelming majority.
But as stated elsewhere in this thread, a lot of cloud providers and virtualization
software default to using BIOS. So I think Fedora should only start considering dropping
BIOS support once the default is UEFI on most virtualization platforms.