No, they would not be able to see the source code or a similar equivalent on a generic decompiler. They can mostly interpret basic math operations, conditionals, and loops, but with anything slightly more advanced they fail at making anything remotely similar to the original code. In the future this may change as they develop better decompilers, but it will likely be some time until anything practical is created.
Newer languages that use interpreters and VMs and such are another story. For instance, any .NET language or Java class can usually be "decompiled" extremely well. ALso, reading IL or bytecode is much simpler than mASM.
