One of the things about Java is that it is stupidly easy to decompile back into java source code.

Obfuscation can make it harder to do but not impossible. There are also performance and licensing implications too.

What it would REALLY hinder is mod development, which is where a huge amount of it's diehard fanbase is, not to mention advertising via let's plays comes from. There's only so much material you can make out of simply building blocks, and the mod scene helps keep Minecraft relevant in Let's Plays and streaming.

The mod scene has been incredibly instrumental in keeping Minecraft as a whole relevant. Most footage and screenshots you tend to see today usually has a mod applied that you can see in the footage. Ever seen Minecraft with realistic lighting? That's a mod. Seen those weird survival challenges? Also done by mods.

If that dies off, Minecraft's word of mouth and relevancy dies with it. And from that, so do the console versions.