Depending on your age, most likely your feet should not get any longer. T won't make bones grow longer that have already "capped". Your feet may get wider, though. Not 100% clear on if it's from increased muscle mass, blood flow changes, or what, but mine widened enough to necessitate larger shoes.
Without knowing your financial situation it's difficult to advise. I don't want to say something like, "Just buy a new pair now and replace it again if you have to", not everyone can afford to go around buying new shoes all the time. You could shoot for a middle ground, look for a pair of shoes in a similar size but with a little wiggle room in case your feet spread. You could check some local thrift stores for shoes in your size so it isn't so much of a blow to the wallet.