Does this mean that the ARM port of MINIX 3 will function on the RPi2 directly?
Almost certainly (for the most part...), since the foundation is flogging it as compatible with various linux ARM distros (Snappy Core Ubuntu), etc., which don't run on the original pi but do run on the BeagleBoard line.
With regard to whatever flavour of linux, this should be as simple as copying the root filesystem image to the second partition of the SD card, putting the kernel into the first one, and adjusting
config.txt there. You'd have to compile the kernel yourself though, in order to make sure it has the drivers it will need to mount the root filesystem built in; this would also apply to MINIX.
Unfortunately I'm guess the pi 2 needs a special driver for the MMC (SD card), as the first one did (it might be the same one); that could be a hassle and may make make MINIX impossible unless you want to write something analagous...or wait for someone else to do it, which may happen.
Excepting that, you could try MINIX easily enough; the pi's bootloader probably won't care what kind of kernel it's loading.1the only complication is getting it to understand where the root filesystem is. With linux this is accomplished via a command-line passed to it by a bootloader; on the pi, that's in
cmdline.txt on the first partition. MINIX might be similar; as something also UNIX derived, the first thing it will want to do after loading is mount the root filesystem and start init.
1. Since that's the role of a bootloader. However, there might be some complication; I guess we will be hearing about this kind of thing soon enough.