Hello,
I've checked and it is not working. The command bootupgrade do nothing. Here is output:
root@NO2-130% ls -al /boot/ total 2996 drwxr-xr-x 4 root wheel 512 Dec 16 20:31 . drwxr-xr-x 12 root wheel 512 Dec 16 20:34 .. -r-xr-xr-x 1 root wheel 785 May 28 2016 bios-autoupgrade.conf drwxr-xr-x 2 root wheel 512 Dec 16 20:31 defaults-r-xr-xr-x 1 root wheel 299308 May 28 2016 loader -r--r--r-- 1 root wheel 7772 May 28 2016 loader.4th -r--r--r-- 1 root wheel 88 May 28 2016 loader.conf -r--r--r-- 1 root wheel 936 May 28 2016 loader.rc drwxr-xr-x 2 root wheel 512 Dec 16 20:31 modules -r--r--r-- 1 root wheel 36440 May 28 2016 support.4th-r-xr-xr-x 1 root wheel 649220 May 28 2016 uboot -r-xr-xr-x 1 root wheel 457144 May 28 2016 ushell root@NO2-130% root@NO2-130% root@NO2-130% bootupgrade -u /boot/uboot -l /boot/loader root@NO2-130%