No supout.rif can be made because that functionality is broken.
On my RB433 it just will sit there with CPU load at 100%, but no file is being generated:
[admin@Jeekim] > sys
[admin@Jeekim] /system> sup
creating supout.rif file, might take a while
.........
Under a RB600A I get:
[admin@Skhal] /system> sup-output
creating supout.rif file, might take a while
.....
Console has crashed; please log in again.
that’s why you have to use beta3 
Sorry to inform you, but CHANGELOG of 5.0beta3 does not mention as addressing nor fixing those type of issues.
Still, I’ve pumped that device to 5.0beta3 and have yet to see that error again.
There is no point to start changelog topic again and again - just be aware the way it is and keep some testing routers to latest versions.
This actually makes life more exiting - lots of unexpected surprises reveal themselves
i’ll just leave this here:
http://forum.mikrotik.com/t/i-cannot-make-a-supout-rif-file-ros-5-b2/37498/1