How much will a 1957 US 1 dollar Silver Certificate be worth in fifty years?

Unfortunately the answer is almost certainly "not much". Huge numbers of 1957 $1 bills were printed in the run-up to introducing $1 Federal Reserve Notes and many of those were saved because they were the last silver certificates. In six decades the value of a 1957 bill in average condition has increased by maybe 50 cents so they're definitely not a good investment, just interesting curiOSities and conversation pieces.