As I understand it the UEFI currently is either 32-bit (x86-32, ARM) or 64-bit (x86-64 and Itanium), but relies on the 16-bit "real mode" interface supported by x86 processors (20-bit address bus).
The UEFI is intrusive enough and already has access to 32/64-bit addressing to the RAM, and to your HDD, etc. So yeah it 'is' happening now.
My take on UEFI - I appreciate the GUI but now that many UEFI's also have 'Games' seem a little CrAzY 'to me.' It makes no difference to me to use a keyboard or mouse to access the BIOS/EFI. The security risks IMO are potentially greater with UEFI, but there are BIOS viruses out there now and I have no doubts UEFI will have it's share.
I can foresee a day when the 'BIOS' and 'OS' merge into some form of 'Firmware' -- Greed will dictate that outcome.
You won't have a 'choice' pretty much every MOBO Mfg is migrating towards UEFI - the gotta have it because it's new and shinny.