That's pretty much what old galvanized pipes look like. I wouldn't do anything unless you have a leak. It's more likely that you'll experience a clog, though, from accumulated corrosion and deposits inside the pipe. Rarely do pipes rust all the way through.
I would plan on replacing as much metal drain pipe as possible when/if you do renovate, though. In my home I cut channels in the slab and replaced most of my galvanized and cast iron with PVC after it started backing up from the kitchen. One two-inch line was down to a finger-sized trickle due to rock hard deposits in the pipe under the floor.