While it's a worry for sure, I don't see such AI creations becoming the mainstream.
Why? Because just like software, game develip needs the inspiration, the creative spark.
Sure you can create a copy of an existing software... But it either doesn't go anywhere (because why would someone want a sloppy copy of a copy of a copy?), or it pivots to actually serving needs that exist on the market.
In other words: an artist or developer with the inspiration, the genuine original idea, will create something actually enjoyable/useful, whereas a copycat will always just be that, someone who saw an idea and decided to copy it without adding anything to it.