You are better off replacing the water pump right now rather than playing the guessing game (how long until it DOES fail). Sure there are a few that make it up to 150k or so before they fail but there are many that don't make it past 120,000. I don't care whether they say the chain can wait till however much longer, the chain puts a lot of vibration through to the water pump bearings and its cheaper to replace them both at the same time than it is to go back and tear the engine apart 50,000 miles later to replace the chain.
I don't mean to annoy you or anything, but most often people don't realize that there water pump is getting ready to take a dump until its too late. Either it'll lock up and take out the timing chain and valve train, or it'll leak like a sieve and by the time the temp gauge tells you that something isn't right, all of the bearings are gone.