could the surviving bombing suspect who was naturalized last Sept 11, 2013 have his citizenship revoked?

We don't revoke citizenship for post-naturalization activities.  Revoking citizenship currently requires proving that there was some misrepresentation in the immigration or naturalization process prior to the benefit being confered.   To allow actions after you become a citizen to put your status at risk creates a class of citizens that do not have the same rights as those who are born here.  There are many policy implications to changing our current citizenship laws.  Stripping someone of their citizenship gains the state no particular advantage since we want to prosecute and punish offenders in our own jurisdiction anyway.