If the belt breaks or the pulley completely separates, you will lose all PS and the alternator. If you use no lights/accessories/brake lights/turn signals and you have a healthy battery, you can go about 1/2 hour without an alternator.
Also if the crank pulley completely separates, it could go in and damage the timing belt cover (no big deal - you'll have a scarred timing belt cover, chicks dig scars
) or press the timing belt cover into the timing belt and knock it off (big deal - car stops running right there).
Even if you can't find someone to help you watch the PS pulley, at least put a line of paint on the pulley to check to see if the separation has started.
I put a line on my non symptomatic pulley and check the line every time I have the hood open.
If the problem lies in the PS pump or rack itself, then yeah, the worst case is you'll lose PS and will have to strong arm it. Not bad for driving... parallel parking is fun....