I think you have answered your own question. You don't need to but after 9 years on the road your water pump can go out at any point. My mechanic almost always suggests it after the 2nd timing belt, if your water pump goes your looking at about a $600 bill. If you do it now with your timing belt, it may add about $175. However I've owned 4 hondas (i own a driving school) and I've never had a honda lose its water pump.
I wouldn't if you don't have the money but rest assured I'd do it when you change the timing belt again.