Why on EARTH would you need a cronjob to do this?

Change it on boot using an /etc/event.d/ script and be done with it. There's no reason you need to constantly echo the value in.

/etc/event.d/region-swap
start on started hildon-desktop
stop on starting shutdown
console none
service

script

echo 4 > /sys/class/i2c-adapter/i2c-2/2-0063/region

end script

And that's it. If you want it controlled by a cronjob, and only run at boot, simply use @reboot.