For this to become a serious issue a couple of conditions need to be met:

• there has to be enough second hand supply to meet demand and keep prices low.
• ...which means lots of people need to circulate their games.
• ...which means they didn't like your game enough to want to keep it in their collection for replayability
• ...which means you made an unremarkable game

Now, given the fact that I have full confidence in your ability to create something worthwhile (because you would do so from passion), this cycle will likely be broken at some point.

There's also the other option where people will circulate their second hand games with the knowledge they'll be able to buy back another copy somewhere down the road.

But yes, you're right that this will bring a new factor to the gaming industry that everyone has to take into account. Keep in mind that your financial security in the indie gaming sector is fully dependant on wether you develop something worthwhile. You are in no way entitled to be able to make a living from publishing games regardless of their quality. Which is the beauty of the indie games segment: the more love and care you put into your game, the bigger the chances are that it'll be a success.