That would be interesting to read @pundito. My belief is that these scientists are basically guessing mostly, because there is no way for them to know for sure.
Everything is theory based on theory on today's way of thinking and with the information they have. And I dont think they have a lot. Were still discovering stuff on Earth.
So there could be a fair chance of them being completely wrong and that somewhere in universe maybe closer than we think there is a world with silicon based life forms.
We will just have to wait for the technology to advance so we can look for the answers.