It's certainly possible, but if this is the "credible threat" theory it might be even worse than a panic closing.
Consider all the "credible threats" we've had over the past year where nothing has happened.
What it might mean is that terrorists don't even need to have real snipers. They just need to have minimal counterintelligence capability to dupe the panic-stricken government into believing something bad might happen. Then they can just sit back and watch the chaos unfold.
Not for long, though. Israelis have adapted and so will we. After all, as everybody keeps repeating: We're at war.