Hey Ghidra was just released, which allows decompilation/disassembly to reveal, then analyze source code.
Wow. Looks like good bye to keeping your code to yourself, I guess. . . .
It's not really that dire. Tools like Ghidra have been available for a long time now, it's just that the most competitive one, IDA, has had a solid grip on the market for some time. IDA Freeware has been available, which has very good disassembly, but limits you on more exotic processor architectures and has no decompilation. The paid version with the decompiler is 5K+ USD (I don't remember the exact number), only because there was no competitor who could challenge them on that. The benefit of Ghidra is that now people can get many of the features of IDA Pro but it's completely free and open source, and the community can improve it. It's not really bringing any tools that didn't exist before into existence.
You also have to consider that, at least for fully ahead of time compiled languages like c++, much of the information in source is lost discarded during compilation, so even with a good decompiler you'll end up with a jumbled mess of code that'll need someone skilled to spend some time discerning what it does and cleaning it up. For something like C# there is much more information in a binary, and without an obfuscator you can get really nice decompiled code with free tools that existed before Ghidra. Using an Obfuscator or maybe figuring out a way to completely ahead of time compile the game before releasing it would probably be the best defense against reverse engineering from what I understand. Of course it won't stop the most determined of people, but it'll raise the bar on skill needed to do so and make it much more time consuming.