This is theoretically possible, but what company (or hobbyist) in their right mind is going to do this and think they can commercialize it when anyone can just give it away?!
Disclaimer - I’m someone with a keen interest in the business possibilities of FLOSS.
+1 for emphasising the unlikelihood of the scenario, but the rest of that paragraph is bordering on FUD. There are a huge number of companies that use GPL code all the time, depending on where it’s going to be used - no problem using it on the server side of a networked game, for example. If it’s network based you could even GPL the client if you control the network (Second Life?) Frankly, all third-party code comes with caveats and implications whatever the license, open or closed - any company that copies third-party code without a clear audit trail deserves all they get, and any employee who does so deserves to be fired!
So tell that to the billion-dollar companies who’ve picked the GPL to achieve what the OP asked for.
I would steer well clear of the “non-commercial” clause. As I mentioned above, there’s an interesting (depending on your definition of interesting
) report on the Creative Commons site about issues with the “non-commercial” clause, and the lack of a cross-jurisdictional legal definition. I’d stick with a license that’s had some legal testing.
+1. There’s a 99.9% chance your code will be ignored anyway - stop worrying about it and get coding! ;D

, you do realise that the code you’d already released would still be open-source, right? Once it’s started making money sounds a little like shutting the stable door after the horse has bolted!