It will not come up in PAL mode unless you do a factory default OR unless there is a problem when the file is loaded.
These updates do not normally write to the var folder, so you should have nothing to worry about.

IF you do end up in PAL, there are several ways to get out of it. The web interface works in PAL so if you have that installed before you update, you can see the receiver's screens and menus on your computer.