As I heard in the last Google I/O the apps running on Android L will be compiled and run on the new ARM. So as far as I understood, will this prevent decompiling apps like it is possible right now? So that not everyone can decompile it and look into the source code?
Android L will have the new ART. Apps will be compiled to native machine code on the device.
So, you are deploying a normal APK, but when the user installs it, it will be compiled to native machine code. I think, as long you can get the APK, decompilation will work fine, otherwise, if you cannot get it, you can still disassemble.