-c arcfouroption anymore. Instead you will receive an error message like:
$ ssh -c arcfour localhost
ssh_dispatch_run_fatal: Connection to ::1: no matching cipher found
The ssh client portion seems to still support RC4 because I seem t be able to still connect to Linux servers that have support for RC4 still enabled but the SSH server portion has RC4 disabled.
I generally like this move because and I think it took apple way to long to obsolete RC4 support. 01/20/2016